What drugs are likely to interfere with urine drug screens? | Drug Information Group (2022)

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Introduction
Abuse and misuse of prescription and illicit drugs is a growing concern, with 11.7% of the U.S. population over 12 years of age reporting illicit drug use in 2018, an increase from 7.9% in 2004.1,2 Drug testing is frequently used in clinical setings to identify substance-use disorders, confirm medication adherence, or identify overdoses. Drug tests are also performed in the workplace to identify illicit substance abuse. Drug testing can be performed using various biologic specimens, including urine, saliva, hair, sweat, nails, meconium, and blood. Urine is most commonly used due to its ease of collection. Additionally, drugs can be detected in the urine for a longer duration compared to blood or serum, and the concentration is typically higher. Both parent and metabolite compounds can be detected in the urine.

When collecting a urine sample, several factors should be recorded to ensure accurate collection and avoid false-negative results, including temperature, pH, specific gravity, and creatinine.2 These factors should be considered when evaluating results to rule out adulterated samples. The temperature of urine should be between 90 to 100 degrees Fahrenheit measured within 4 minutes of collection; the pH should be consistent with the range of 4.5 to 8; the specific gravity should be between 1.002 and 1.030; and the creatinine should be greater than 20 mg/dL. Certain medications, foods, and disease states may cause valid outliers; however, a pH <3 or >11 or a specific gravity <1.002 or >1.030 increases the suspicion for adulteration.

Methods for urine drug testing
There are 2 main methods for urine drug testing, screening and confirmatory.2 Immunoassay testing is primarily used for initial screening. Immunoassay testing can be performed in a laboratory or in an office using point of care testing. Results are relatively rapid, and the test can screen for a wide variety of drug metabolites. The 3 most common types of immunoassay testing include enzyme-multipled immunoassay technique, enzyme-linked immunosorbent assay (ELISA), and fluorescence polarization immunoassay. Immunoassay technology uses antibodies to detect drug metabolites. However, antibodies may detect drug metabolites with similar structure and characteristcis, leading to false-positive results. For this reason, immunoassay testing should be considered preliminary and presumptive.

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Confirmatory testing should be considered following a presumptive positive screening test.2 The decision to perform a confirmatory test should take into consideration the patient’s history, clinical judgement, and the potential impact on patient care. Confirmatory tests are more timely and costly and are performed by highly trained laboratory personnel. Gas chromatography/mass spectrometry (GC-MS) is the gold standard for confirmatory testing. This test is more specific than immunoassay testing, as it detects drugs by molecular structure. Additionally, GC-MS quantifies the amount of drug present in a sample. Liquid chromatography/tandem mass spectrometry (LC-MS/MS) is an alternative to GC-MS and may be more time efficient.

Quantification of urine drug levels
Drug concentration level thresholds are used in reporting of positive and negative reports for urine drug testing.2 If a test detects a concentration above the threshold, it is reported as positive, and vice versa for negative results. Cutoff values were developed to mitigate false-positive results, especially in the workplace. The use of cutoff values may be particularly useful in ruling out false-positives due to passive inhalation of substances. The U.S. Department of Health and Human Services (DHHS) standardized these cutoff values for drug testing in the workplace (Table 1).3,4 A negative test result using these values does not represent the absence of drug use, and false-negatives can occur.2 Lower thresholds may be used in clinical settings, as the cutoff values defined by the DHHS are higher and intended for the workplace. For example, testing for medication adherence would necessitate lower thresholds. The DHHS cutoff values were developed for adults, and lower thresholds should be used for infants. Infants tend to have more dilute urine, which reaches adult osmolarity around the age of 2 years. In 1998, the DHHS increased the cutoff for opiates from 300 ng/mL to 2000 ng/mL to avoid false positive tests from poppy seed ingestion, as well as routine prescription drug use. Synthetic and semisynthetic opioids historically have not been included as part of federal workplace drug testing; however, in 2017 the U.S. DHHS released cutoffs for hydrocodone/hydromorphone and oxycodone/oxymorphone for additional testing.5

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Table 1. U.S. DHHS drug testing cuttoff values for adults in the workplace.4,5
Initial test (immunoassay)
Confirmatory test (GC-MS)
Analyte
Cutoff concentration
Analyte
Test cutoff
Marijuana metabolites
50 ng/mL
THCA
15 ng/mL
Cocaine metabolites
150 ng/mL
Benzoylecgonine
100 ng/mL
Codeine/Morphinea2000 ng/mL
Codeine
2000 ng/mL
Morphine2000 ng/mL
Hydrocodone/hydromorphone
300 ng/mL
Hydrocodone
100 ng/mL
Hydromorphone100 ng/mL
Oxycodone/oxymorphone
100 ng/mL
Oxycodone
100 ng/mL
Oxymorphone100 ng/mL
6-Acetylmorphine10 ng/mL
6-Acetylmorphine
10 ng/mL
PCP
25 ng/mL
PCP
25 ng/mL
Amphetamine/ Methamphetamineb500 ng/mL
Amphetamine
250 ng/mL
Methamphetaminec250 ng/mL
MDMA
500 ng/mL
MDMA
250 ng/mL
MDA
250 ng/mL
MDEA
250 mg/mL
aMorphine is the target analyte for codeine/morphine testing.
bMethamphetamine is the target analyte for amphetamine/methamphetamine testing.
cSpecimen must also contain amphetamine at a concentration greater than or equal to 100 ng/mL.
Abbreviations: DHHS=Department of Health and Human Services; GC-MS=gas chromatography-mass spectrometrey; MDA=methylenedioxyamphetamine; MDEA=methylenedioxyethylamphetamine; MDMA=methylenedioxymethamphetamine; PCP=phencyclidine; THCA=delta-9-tetrahydrocannabinol-9-carboxylic acid.

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Drug detection times
Each drug varies in the amount of time it can be detected in the urine (Table 2).2 The detection time is primarily based on half-life and the presence of drug metabolites. Additional factors such as drug interactions, dose and frequency intervals, chronic versus occasional use, and time of last ingestion can all affect the detection window. Patient variability in body mass, urine pH and concentration, and renal and hepatic function can also affect the detection window.

Table 2. Length of time drugs can be detected in the urine.2
Drug/drug class
Detection timeDrug/drug class (continued)
Detection time
Alcohol
7 to 12 hoursMarijuana
Single use
Moderate use (4x/week)
Daily use
Long-term heavy smoker

3 days
5 to 7 days
10 to 15 days
>30 days
Amphetamine
48 hours
Methamphetamine
48 hours
Barbiturates
Short-acting
Long-acting

24 hours
3 weeks
Benzodiazepines
Short-acting
Long-acting

3 days
30 days
Opiates
Codeine
Heroin (morphine)
Hydromorphone
Methadone
Morphine
Oxycodone

48 hours
48 hours
2 to 4 days
3 days
48 to 72 hours
2 to 4 days
Cannabinoids, synthetic
Single use
Chronic use

72 hours
>72 hours
Cocaine metabolites
2 to 4 daysPCP (Phencyclidine)
8 days

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False-positive results
Due to the potential for cross-reactivity associated with immunoassay urine drug screens, several prescription and non-prescription drugs have been reported to cause false-positive results.2,6 In addition to medications, several other substances have been associated with false-positives, such as baby wash products, supplements, and food. False-positive drug screens are commonly documented in case reports. Various immunoassay drug tests are available on the market, and each test uses a proprietary antibody technology, leading to differences in false-positive results between tests.7 Furthermore, immunoassays may be reformulated to correct for false-positive, which may not be adequately reflected in published literature. For example, an immunoassay for cannabinoids that resulted in a false-positive from ibuprofen was corrected over 20 years ago. Ibuprofen is still frequently reported in resources as a possible cause for false-positive cannabinoid immunoassays. Table 3 lists substances that may cause false-positive results on immunoassay urine drug screens; however, this list may not include all potential substances.2, 8-10 Positive immunoassay urine drug screens should be considered presumptive, and confirmed with GC-MS to rule out false-positives.

(Video) How long are different drugs detectable in your system - urine testing, hair testing, etc.

Barbiturate tests are generally reliable, and false-positives and -negatives are rare.5 Similarly, immunoassays for cocaine are sensitive and specific. In general passive inhalation of crack cocaine does not cause a false-positive; however, it has been reported in cases of chronic exposure.

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Table 3. Substances that may cause false-positives on immunoassay urine drug screens.2, 8-10
Drug/drug class
Interfering medication
Amphetamine
Amantadine, aripiprazole, atomoxetine, brompheniramine, bupropion, chlorpromazine, desipramine, DMAA, ephedrine, fluoxetine, labetalol, metformin, ofloxacin, phentermine, phenylephrine, phenylpropanolamine, promethazine, pseudoephedrine, ranitidine, selegiline, thioridazine, trazodone, nonprescription nasal antihistamine/decongestant inhalation
Barbiturates
Ibuprofen, naproxen
Benzodiazepines
Efavirenz, oxaprozin, sertraline
Buprenorphine
Amisulpride, sulpride, tramadol
Cannabinoid
Baby wash products, dronabinol, efavirenz, ibuprofen, lamotrigine (on screenings for synthetic cannabinoids), naproxen, niflumic acid, proton pump inhibitors
CocaineaCoca leaf tea
LSD
Ambroxol, amitriptyline, benzphetamine, bupropion, buspirone, cephradine, chlorpromazine, desipramine, diltiazem, doxepin, fentanyl, fluoxetine, haloperidol, imipramine, labetalol, metoclopramide, prochlorperazine, risperidone, sertraline, thioridazine, trazadone, verapamil, ergonovine, lysergol, brompheniramine, imipramine, methylphenidate, fentanyl, sertraline
Methadone
Diphenhydramine, doxylamine, chlorpromazine, clomipramine, doxylamine, quetiapine, thioridazine, verapamil
Opiates
Amisulpride and sulpride, codeine, dextromethorphan, diphenhydramine, dihydrocodeine, morphine, methadone, morphine-3-glucuronide, creatinine, dihydrocodeine, levofloxacine, ofloxacine, morphine, naloxone, ofloxacin, petanzocine, psychotropic drugs, quetiapine, rifampicin, tapentadol, tramadol, verapamil, quinolones, quinine
PCP
Dextromethorphan, diphenhydramine, doxylamine, ibuprofen, imipramine, ketamine, lamotrigine, MDPV, meperidine, thioridazine, tramadol, venlafaxine
TCAsbCyclobenzaprine, quetiapine
aAmoxicillin has been reported to cause false-positives in review articles and various internet sources; however, data is lacking to confirm this cross-reactivity.
bFalse-positives in the serum have been reported for carbamazepine, cyproheptadine, diphenhydramine, and hydroxyzine.
Abbreviations: DMAA=dimethylamylamine (an energy supplement); LSD=lysergic acid diethylamide; MDPV=3,4-methylenedioxypyrovalerone (synthetic cathinone in bath salts); PCP=phencyclidine; TCA=tricyclic antidepressant

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False-negative results
In addition to false-positive results, there are several notable limitations of immunoassay urine screens that can lead to false-negative results.6 Enzyme immunoassays used for amphetamines have low sensitivity to certain drugs commonly used in the “rave scene”, such as 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyamphetamine (MDMA), and they are unable to detect phenethylamine-based “bath salts”. Benzodiazepines also are regulary missed on enzyme immunoassay screens. Benzodiazepine use may result in low concentration levels that are not detected on screening, which is common for clonazepam. Additionally, many enzyme immunoassays are designed to detect nordiazepam or oxazepam, metabolites of diazepam, chlordiazepoxide, and clorazepate.11 Therefore, lorazepam and clonazepam are not reliably detected by immunoassay, and GC-MS should be utilized if detection of these agents is desired. Many positive phencyclidine (PCP) tests are due to cross-reactivity; given that it is no longer commonly abused in the U.S., with the exception of select regions, clinical presentation should be used to guide management without the use of an immunoassay drug screen.6 Immunoassays for tetrahydrocannabinol (THC) are not able to detect newer synthetic cannabinoids. Opiate immunoassays detect morphine and codeine, the major metabolites of heroin and a common contaminant acetylcodeine, respectively.11 Therefore, they do not reliably detect semisynthetic and synthetic opioids. Additionally, it is important to note which opioids are included on an institution’s standard screening, as certain opioids may require an additional order or GC-MS.

(Video) How Accurate Are Drug Tests?

Summary
While urine drug screening using immunoassay is convenient, the test is associated with multiple limitations. An understanding of these limitations is necessary to identify false-positive and false-negative results. Additionally, a thorough medication history should be obtained to anticipate false-positive results. In addition to medications, certain body washes, foods, and supplements have been associated with false-positives, which may be difficult to identify. Positive results on urine immunoassay screening should be considered presumptive, and confirmatory testing with GC-MS should be considered to confirm the findings.

References

  1. Illicit drug use. Centers for Disease Control and Prevention (CDC). Updated March 1, 2021. Accessed April 8, 2021. https://www.cdc.gov/nchs/fastats/drug-use-illicit.htm
  2. Moeller KE, Kissack JC, Atayee RS, Lee KC. Clinical interpretation of urine drug tests: what clinicians need to know about urine drug screens. Mayo Clin Proc. 2017;92(5):774-796. doi: 10.1016/j.mayocp.2016.12.007
  3. Drug-free workplace guidelines and resources. Substance Abuse and Mental Health Services Administration (SAMHSA). Updated March 15, 2021. Accessed April 8, 2021. https://www.samhsa.gov/workplace/resources
  4. Analytes and their cutoffs. Substance Abuse and Mental Health Services Administration (SAMHSA). Analytes. November 25, 2008. Accessed April 8, 2021. https://www.samhsa.gov/sites/default/files/workplace/2010GuidelinesAnalytesCutoffs.pdf
  5. Mandatory guidelines for federal workplace drug testing programs. Substance Abuse and Mental Health Services Administration (SAMHSA). January 23, 2017. Accessed April 8, 2021. https://www.federalregister.gov/documents/2017/01/23/2017-00979/mandatory-guidelines-for-federal-workplace-drug-testing-programs
  6. Nelson ZJ, Stellpflug SJ, Engebretsen KM. What can a urine drug screening immunoassay really tell us? J Pharm Pract. 2016; 29(5):516-26. doi: 10.1177/0897190015579611
  7. Grunbaum AM, Rainey PM. Laboratory principles. In: Nelson LS, Howland M, Lewin NA, Smith SW, Goldfrank LR, Hoffman RS, eds. Goldfrank’s Toxicologic Emergencies. 11th ed. McGraw-Hill; 2019: chap 7. Accessed April 8, 2021. https://accesspharmacy.mhmedical.com/content.aspx?sectionid=210267566&bookid=2569#216818178
  8. Saitman A, Park HD, Fitzgerald RL. False-positive interferences of common urine drug screen immunoassays: a review. J Anal Toxicol. 2014;38(7):387-369. doi: 10.1093/jat/bku075
  9. Brahm NC, Yeager LL, Fox MD, Farmer KC, Palmer TA. Commonly prescribed medications and potential false-positive urine drug screens. Am J Health Syst Pharm. 2010;67(16):1344-1350. doi: 10.2146/ajhp090477
  10. Standridge JB, Adams SM, Zotos. Urine drug screening: a valuable office procedure. Am Fam Physician. 2010;81(5):635-640.
  11. Cupp M. PL Detail-Document, urine drug testing. Pharmacist’s Letter/Prescriber’s Letter. March 2014.

Prepared by:
Amanda Gerberich, PharmD, BCPS
Clinical Assistant Professor, Drug Information Specialist
University of Illinois at Chicago College of Pharmacy

May 2021

The information presented is current as April 5, 2021. This information is intended as an educational piece and should not be used as the sole source for clinical decision making.

(Video) Chemistry: Drug of Abuse Urine Screening Test (DAU)

FAQs

What can cause a false positive on a urine drug screen? ›

Clinically, a false positive urine drug screen can be due to numerous xenobiotics: dextromethorphan, diphenhydramine, doxylamine, ibuprofen, imipramine, ketamine, meperidine, venlafaxine, buproprion, methylenedioxpyrolvalerone (MDPV), and tramadol.

What can cause a false negative drug test? ›

Causes of potentially inappropriate negative UDT results include limited assay specificity, absence of drug in the urine, presence of drug in the urine, but below established assay cutoff, specimen manipulation and laboratory error.

What should you not do before a urine test? ›

- Avoid alcohol, coffee, tea, tobacco and strenuous exercise for 24 hours prior to collection and up to collection time. - Do not consume avocados, bananas, eggplant, pineapples, plums, tomatoes or walnuts for 48 hours before the test.

How long before a urine test should I drink water? ›

The only thing that affects a dilute sample is the amount of fluid taken in within a short period of time prior to providing the urine sample. If you are seeing results that show you are getting close to a dilute sample, try to stop drinking any fluids 2-4 hours prior to providing the sample.

What foods can cause false positive drug test? ›

Some foods, drinks, and prescription medications contain the necessary chemicals and metabolites to trigger a false-positive.
  • Poppy Seeds. ...
  • Pizza. ...
  • Durian. ...
  • Hemp Seeds – Granola Bars. ...
  • A Cup of Coca Tea. ...
  • Tonic Water. ...
  • Ibuprofen. ...
  • Antibiotics.
14 Aug 2020

Can ibuprofen cause false positive on drug test? ›

Nonsteroidal anti-inflammatory drugs (NSAIDs) have also been shown to interact with UDS immunoassays. Both ibuprofen and naproxen have been documented to cause false-positive barbiturate4 and cannabinoid1-4 levels. In addition, ibuprofen can cause a false-positive PCP level.

Can Tylenol cause false positive drug test? ›

You should also be aware that certain antidepressants like Zoloft and Prozac, along with sleeping pills like Tylenol can cause a false positive. Anyone taking OTC or prescription medications should raise the matter immediately after a false positive.

Does adding salt to urine affect drug test? ›

Table salt: Drug binding by changing protein structures [11]. Therefore, table salt affects the immunassay results and its high doses produce false negative results. Studies have shown that sodium chloride increases urine density, which is one of the urine validation tests [12].

How common are false negatives on drug tests? ›

Drug tests generally produce false-positive results in 5% to 10% of cases and false negatives in 10% to 15% of cases, new research shows.

Will antidepressants show up on a drug test? ›

Antidepressants do not show up as antidepressants on standard drug tests. The lab would have to do specific additional tests to look for antidepressants. Sometimes, however, an antidepressant will trigger a false positive on a drug test, showing up on the test as an amphetamine or lysergic acid diethylamide (LSD).

When's the best time to take a urine sample? ›

You can collect a urine sample at any time of day, unless your GP or practice nurse advises you otherwise. The types of urine sample you might be asked for include a random specimen, first morning specimen or timed collection.

What substances should not be found in urine? ›

Usually, glucose, ketones, protein, and bilirubin are not detectable in urine.

What are 4 types of tests done on urine? ›

The following substances can be checked using a rapid urine test:
  • pH value (measure of the acidity of the urine. ...
  • Protein (not usually found in urine)
  • Sugar (glucose, not usually found in urine)
  • Nitrite (not usually found in urine)
  • Ketone (a metabolic product, not usually found in urine)
27 Jul 2010

Can drinking too much water affect urine test? ›

Internal Adulteration

Drinking large volumes of just about any non-toxic water-based liquid will dilute urine. Drinking two or three 12-ounce glasses of water at the same time can produce 10-fold diluted urine within only half an hour and the dilution effect may last for hours.

How much water should I drink to clear my system? ›

“Drink 20 to 40 ounces of sports drink per day to restore your electrolytes and keep you hydrated. Drink roughly 1 gallon (3.8 L) of water to flush your body of toxins.

Will 2 liters of water dilute urine? ›

Typically ingesting 1-2 liters or more within an hour of testing is sufficient to dilute most specimens for a 2–6 hour period. Diuretics such as caffeine and cranberry juice and some medications, including water pills may cause diluted urine samples.

What is the most common false positive drug test? ›

False-positive results for amphetamine and methamphetamine were the most commonly reported. False-positive results for methadone, opioids, phencyclidine, barbiturates, cannabinoids, and benzodiazepines were also reported in patients taking commonly used medications.

Can I drink coffee before a drug test? ›

If your doctor has ordered a test for metanephrine in your urine, you should avoid caffeine for 24 hours and during collection of your specimen.

How much ibuprofen causes false positive? ›

Ibuprofen

Once ingested, it takes around three hours for ibuprofen to lead to a false positive of cannabis, barbiturates, and PCP in your urine. The wrong positive shows for people whose consumption falls within the range of 800 to 1200 milligrams per day.

How much Benadryl will cause a false positive? ›

The critical concentration level for diphenhydramine capsules was 1 mg/mL, for diphenhydramine tablets 2.5 mg/mL, methamphetamine was 1.5 mg/mL, and MDMA was 2 mg/mL. At or above these concentrations, the FTS is likely to produce a false positive result.

Will ibuprofen 800 mg make you fail a drug test? ›

Analgesics/ NSAIDS

Common over-the-counter anti-inflammatory pain medications such as Advil (ibuprofen) and Aleve (naproxen) could make you test positive for barbiturates and THC (marijuana/cannabinoids); and ibuprofen can also make you test positive for PCP.

How do I dispute a positive drug test? ›

How Can I Dispute a False Positive Drug Test?
  1. Step 1: Get out in front of the issue. ...
  2. Step 2: Ask your doctor or pharmacist. ...
  3. Step 3: Ask to retake the drug test.
2 Jul 2021

What's the most accurate drug test? ›

Blood tests are the most accurate drug tests but are also the most expensive option. Another challenge with blood tests is that drugs do not stay in the blood long; for example, marijuana only stays in the blood for a few hours after a single use and stays for 24 hours for chronic users.

Should I bring my prescriptions to a drug test? ›

I would suggest bringing your prescription with you for the testing and allow the person doing the test to write down the pertinent information, such as doctor's name, prescription expiration, refills, etc. so this can be included in the report if necessary.

Can Adderall cause you to fail a drug test? ›

The use of Adderall can cause a patient to test positive for amphetamine but not methamphetamine. Amphetamine does not metabolize to methamphetamine.

Are lab drug tests harder to pass? ›

What about accuracy? Lab-based drug tests are more accurate. We like to say they are more rigorous, more involved, and more defensible in a court of law, all of which are elements certain organizations must consider, particularly heavily regulated industries, like the DOT.

What is clean catch method? ›

A clean catch is a method of collecting a urine sample to be tested. The clean-catch urine method is used to prevent germs from the penis or vagina from getting into a urine sample.

How long will delta 8 stay in your system for a drug test? ›

Last Words. While delta-8 THC's effects last up to five hours in your body, the metabolites can stay in your system for up to 90 days. Luckily, the most common tests can detect metabolites for only a few days. However, if you are a chronic user, the test can yield positive even after 30 days.

How do you adulterate a urine drug test? ›

Common adulterants used to mask drug testing
  1. Table salt (sodium chloride).
  2. Household vinegar (acetic acid).
  3. Liquid laundry bleach (sodium. hypochlorite).
  4. Concentrated lemon juice.
  5. Goldenseal tea (produces dark urine).
  6. Diluted urine (creatinine below 15. mg/mL).
  7. Visine eye drops (interfere mostly with EMIT assay).
1 Feb 2003

Can I take Tylenol before a drug test? ›

All NSAIDs can cause a false positive. Alternatives to ibuprofen such as aspirin and acetaminophen don't cause the same effect and are safe to use before a drug screen.

Will Zoloft show up in a urine test? ›

Zoloft (brand name of sertraline) is commonly prescribed as a treatment for depression, anxiety, PTSD, OCD, premenstrual dysphoric disorder, and panic attacks. This medication is not typically targeted on drug tests. It can, however, produce false-positive test results for illicit substances.

What foods can cause false positive drug test? ›

Some foods, drinks, and prescription medications contain the necessary chemicals and metabolites to trigger a false-positive.
  • Poppy Seeds. ...
  • Pizza. ...
  • Durian. ...
  • Hemp Seeds – Granola Bars. ...
  • A Cup of Coca Tea. ...
  • Tonic Water. ...
  • Ibuprofen. ...
  • Antibiotics.
14 Aug 2020

Can ibuprofen cause false positive on drug test? ›

Nonsteroidal anti-inflammatory drugs (NSAIDs) have also been shown to interact with UDS immunoassays. Both ibuprofen and naproxen have been documented to cause false-positive barbiturate4 and cannabinoid1-4 levels. In addition, ibuprofen can cause a false-positive PCP level.

Can period blood affect urine drug test? ›

What might affect my test results? Menstrual blood can contaminate a urine sample.

Will menstrual blood affect urine test? ›

If you're menstruating (on your period), it's important to let your provider know before collecting your urine sample. Menstrual blood, as well as vaginal discharge, can interfere with certain urinalysis test results.

What is the most common false positive drug test? ›

False-positive results for amphetamine and methamphetamine were the most commonly reported. False-positive results for methadone, opioids, phencyclidine, barbiturates, cannabinoids, and benzodiazepines were also reported in patients taking commonly used medications.

Can I drink coffee before a drug test? ›

If your doctor has ordered a test for metanephrine in your urine, you should avoid caffeine for 24 hours and during collection of your specimen.

What percentage of drug tests are false positive? ›

Drug tests generally produce false-positive results in 5% to 10% of cases and false negatives in 10% to 15% of cases, new research shows.

How much Benadryl will cause a false positive? ›

The critical concentration level for diphenhydramine capsules was 1 mg/mL, for diphenhydramine tablets 2.5 mg/mL, methamphetamine was 1.5 mg/mL, and MDMA was 2 mg/mL. At or above these concentrations, the FTS is likely to produce a false positive result.

Will ibuprofen 800 mg make you fail a drug test? ›

Analgesics/ NSAIDS

Common over-the-counter anti-inflammatory pain medications such as Advil (ibuprofen) and Aleve (naproxen) could make you test positive for barbiturates and THC (marijuana/cannabinoids); and ibuprofen can also make you test positive for PCP.

Will Tylenol Extra Strength show up on a drug test? ›

The acetaminophen/paracetamol assay will yield positive results when acetaminophen/paracetamol is ingested at or above therapeutic doses. The laboratory often receives phone calls asking how long a particular drug of abuse can be detected in urine.

How does vitamin C affect urine drug test? ›

Vitamin C spiking of urine demonstrated false-negative results at various concentrations. Of 159 specimens with positive results for vitamin C, 14 showed discrepant results after additional confirmatory tests. Conclusions: Vitamin C in urine can cause significant interference with urine strip tests.

How long do drug test results take? ›

Beforehand, the trained collection officer will interpret the analysis from the urine cup. Next, and depending if authorisation is in place, they will send the same sample to the laboratory for analysis. The detection window for urine in the system is around 3-5 days depending on the drug.

What are normal urine test results? ›

Normal values, depending on diet, range from about 5 to 7, where values under 5 are too acidic, and values over 7 are not acidic enough) Protein (not usually found in urine) Sugar (glucose, not usually found in urine) Nitrite (not usually found in urine)

What does SG stand for in a urine test? ›

Urine specific gravity is a laboratory test that shows the concentration of all chemical particles in the urine.

What pyuria means? ›

Pyuria is a condition defined by the increased presence of white blood cells in urine. Although a urinary tract infection is the most common cause of sterile pyuria, other conditions may be involved. Doctors define pyuria as the presence of 10 white blood cells in each millimeter cube of the urine.

What are some examples of abnormal findings in a urinalysis? ›

Things the dipstick test can check for include:
  • Acidity, or pH. If the acid is abnormal, you could have kidney stones, a urinary tract infection (UTI), or another condition.
  • Protein. This can be a sign your kidneys aren't working right. ...
  • Glucose. ...
  • White blood cells. ...
  • Nitrites. ...
  • Bilirubin. ...
  • Blood in your urine.
14 Aug 2022

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Introduction: My name is Arielle Torp, I am a comfortable, kind, zealous, lovely, jolly, colorful, adventurous person who loves writing and wants to share my knowledge and understanding with you.