Codeine does show up on standard drug tests, because the basic opiate screen is designed to detect it. A positive result isn’t the end of the story for people taking it as prescribed, since workplace results pass through a doctor’s review before anyone is told. And because the body turns some codeine into morphine, a codeine user’s report can list morphine too, which surprises many people.
How a Standard Drug Test Picks Up Codeine
Most workplace tests start with a quick urine screen for opiates. It reacts to codeine, morphine, hydrocodone, hydromorphone, and a heroin marker.1Mayo Clinic Proc.. Interpretation of Opiate Urine Drug Screens Many of these screens use antibodies that react to a group of related opiate molecules rather than one named drug. So a screen alone shows only that some opiate is present, not which one. A few non-opiate compounds can occasionally trigger a screen, which is one reason a positive screen is never treated as final.
A positive screen goes to a lab confirmation test that measures each drug separately.2Clinical Chemistry. A Practical Approach to Determine Cutoff Concentrations for Opiate Testing with Simultaneous Detection of Codeine, Morphine, and 6-Acetylmorphine in Urine Confirmation usually uses mass spectrometry, which separates a sample into individual molecules and identifies each by its chemical signature. That is how a lab can report codeine and morphine as separate lines with separate concentrations.
A common screening cutoff level is 300 ng/mL, the amount in urine needed to call the sample positive.3PubMed. Forensic drug testing for opiates. V. Urine testing for heroin, morphine, and codeine with commercial opiate immunoassays Some federal workplace programs use a higher screening cutoff of 2,000 ng/mL, which means small amounts can pass as negative.
On a lab report, the screen line may simply say “opiates.” The confirmation line usually names codeine and may name morphine, each with a number in ng/mL, which is the concentration found. “Negative” means below the cutoff level, not necessarily zero. After a codeine dose, codeine is typically the larger number and morphine the smaller one, because only a fraction of codeine becomes morphine. The review doctor reads the two together, and codeine with a modest amount of morphine fits someone taking codeine.
Why Codeine Can Show Up as Morphine
The liver turns some codeine into morphine, which is what gives codeine its pain relief.4PubMed. Codeine intoxication associated with ultrarapid CYP2D6 metabolism In most people only about 5 to 10% of codeine takes this route.5Clinical Pharmacology & Therapeutics. Clinical Pharmacogenetics Implementation Consortium Guidelines for Codeine Therapy in the Context of Cytochrome P450 2D6 (CYP2D6) Genotype Morphine on a report is therefore expected after codeine. It is not a sign of a second drug, and reviewers know the pattern.
Small amounts of hydrocodone can appear too, usually under 11% of the codeine level.6Mayo Clinic Laboratories. Opiates A reviewer can see this fits the codeine pattern rather than a separate prescription.
Late in clearance, a urine sample can show morphine with no codeine at all.7PubMed. Forensic drug testing for opiates, III. Urinary excretion rates of morphine and codeine following codeine administration Even so, a lot of morphine with no codeine is harder to explain by codeine alone, which is where the timing of your last dose matters.
If your report shows morphine and you took codeine, tell the review doctor you took codeine and when you last took it. Don’t assume you’ve been accused of using morphine.
How Long Codeine Stays Detectable
- Urine: about 1.5 to 2 days on average at the 300 ng/mL cutoff, up to about 3 days.8PubMed. Forensic drug testing for opiates. V. Urine testing for heroin, morphine, and codeine with commercial opiate immunoassays
- Saliva: up to about 4 days.9Addiction Center. How Long Do Drugs Stay In Your System?
- Blood: up to about 24 hours.10Addiction Center. How Long Do Drugs Stay In Your System?
- Hair: up to about 90 days.11Addiction Center. How Long Do Drugs Stay In Your System?
These windows are averages from studies, so your own clearance could be shorter or longer. The cutoff level matters too: a test with a lower cutoff level keeps finding codeine longer than one with a higher cutoff level, even in the same person on the same day.
Liquid codeine can leave very high levels in the mouth for the first couple of hours.12PubMed. Correlation of saliva codeine concentrations with plasma concentrations after oral codeine administration After that saliva levels fall at the same pace as blood, roughly halving every 3 hours.13PubMed. Correlation of saliva codeine concentrations with plasma concentrations after oral codeine administration
Hair works on a delay. Codeine reaches hair roots within 30 minutes, but it takes about a week to show up in the hair that’s cut for testing.14PubMed. Testing human hair for drugs of abuse. I. Individual dose and time profiles of morphine and codeine in plasma, saliva, urine, and beard compared to drug-induced effects on pupils and behavior A hair test won’t catch yesterday’s dose but can catch one from weeks ago.15PubMed. Codeine disposition in human hair after single and multiple doses One 120 mg dose stayed detectable in hair at least 10 weeks.16PubMed. Codeine disposition in human hair after single and multiple doses
Kidney disease slows things down. In people on dialysis, codeine’s half-life stretched to about 19 hours versus 4 in healthy people.17PubMed. Pharmacokinetics and pharmacodynamics of codeine in end-stage renal disease Kidney patients may test positive for much longer.
A single dose clears faster than weeks of regular dosing, because repeated doses build up more drug in the body. Higher doses also last longer.
Drinking a lot of water just before a test makes urine very dilute, and labs check for this. A sample flagged as dilute may be rejected or called for a recollection. Stopping prescribed medicine early without your doctor can cause pain or withdrawal; disclosing the prescription is the safer route.
What Happens If You Have a Codeine Prescription
A lab positive goes first to a Medical Review Officer (MRO), a doctor who reviews results before the employer sees them.18Substance Abuse and Mental Health Services Administration. 2024 Medical Review Officer Case Studies – Urine The review doctor interviews you and asks for proof such as a prescription or medical record.19Substance Abuse and Mental Health Services Administration. 2024 Medical Review Officer Case Studies – Urine Under US transport rules, morphine or codeine below 15,000 ng/mL in urine is verified positive only without a legitimate medical explanation.20Office of Drug and Alcohol Policy & Compliance. DOT Rule 49 CFR Part 40 Section 40.139 A genuine prescription normally turns the result into a negative report. Very high levels, at or above 15,000 ng/mL in urine or 150 ng/mL in saliva, are presumed positive unless you prove a medical reason.21Office of Drug and Alcohol Policy & Compliance. DOT Rule 49 CFR Part 40 Section 40.139
A positive explained by your prescription typically never reaches your employer as a positive. The reviewer generally doesn’t pass along your diagnosis or medication, only whether the result is verified negative or positive.
The call often comes a day or several days after the test. Once you’re told of a positive, you’re typically given a limited window to respond, so return it promptly. Missing the call can lead to a positive report. Have your prescription bottle, pharmacy record, and doctor’s name ready, and be ready to give the drug name, the dose, how often you take it, and when you last took it. Saying you have a prescription isn’t enough on its own; the reviewer may phone the prescriber or pharmacy to confirm it.
Some situations don’t settle so easily. A prescription written for another person doesn’t count as yours, even for the same medicine. An old leftover prescription may be questioned if its date falls long before the test and doesn’t fit the timing of your use. In safety-sensitive jobs like driving or operating machinery, a verified negative can still be followed by an employer question about whether you’re fit to work on a sedating drug. Probation and court programs often run their own testing under their own rules, so ask your probation officer how prescriptions are handled before you test, not after.
Poppy Seeds, Antibiotics and Other Look-Alikes
Eating poppy seeds can put real codeine in urine.22PubMed. Morphine and codeine concentrations in human urine following controlled poppy seeds administration of known opiate content Poppy seeds can carry traces of codeine and morphine, so a confirmation test can’t tell a poppy seed result from a medication result by itself. The amount depends on the seeds, since some are less washed or processed than others, and on how much you eat, so the same bagel can produce different results for different people.
After controlled poppy seed meals, about 1 in 5 urine samples passed 300 ng/mL of codeine.23PubMed. Morphine and codeine concentrations in human urine following controlled poppy seeds administration of known opiate content None reached the 2,000 ng/mL cutoff used in many workplace programs.24PubMed. Morphine and codeine concentrations in human urine following controlled poppy seeds administration of known opiate content If you’re already taking codeine as prescribed, seeds add little, because your own dose is the far bigger source.
Some quinolone antibiotics, like levofloxacin and ofloxacin, can make a urine opiate screen falsely positive.25PubMed. Quinolones and false-positive urine screening for opiates by immunoassay technology A confirmation test should clear it.26PubMed. False-positive urine opiate screening associated with fluoroquinolone use If your confirmation did show codeine or morphine, the antibiotic doesn’t explain it, since it only affects the screen. Being around other people’s medication is unlikely to cause a positive.27The Journal of Family Practice. What common substances can cause false positives on urine screens for drugs of abuse?