How long does a drug work, and how long does it stay detectable?

Snorted cocaine works for roughly thirty to sixty minutes. A lab still sees it days later. Those two sentences do not contradict each other, and the gap between them explains almost every confusion people have about drug testing.

Because a lab does not measure cocaine. It measures benzoylecgonine, the breakdown product your liver makes from it, and that hangs around far longer than the drug itself (PMID 11043648).

I find that the most underrated fact in toxicology. People assume a test measures what they felt. A test measures what their body kept.

How long does cocaine work?

Snorted cocaine starts working within minutes and the effect has largely faded after thirty to sixty minutes. Smoked, it is faster and shorter still. That short duration is exactly why people redose so quickly, often before the previous effect has fully worn off.

The high is short. The trace you leave behind is not.

Cocaine itself largely clears your blood within hours. Benzoylecgonine, its main metabolite, has a much longer half-life and accumulates with repeated use. In volunteers given cocaine repeatedly, benzoylecgonine remained measurable in urine for days after the final dose (PMID 11043648).

Why is a drug gone in hours but detectable for days?

Because working and being detectable are two different processes. A drug works for as long as it binds receptors in your brain. It is detectable for as long as the drug or its breakdown products are still somewhere in your body, and that can outlast the feeling by a wide margin.

Your liver breaks almost every substance down into metabolites. Those metabolites have their own half-life, their own exit route and their own concentration in urine, blood or hair. For some substances the metabolite is more stable and more soluble than the parent drug, and that breakdown product becomes the signature the lab looks for.

That is not a trick of the lab. It is simply what is left.

How that breakdown process works step by step is covered in our piece on how your body breaks down drugs and alcohol.

What does a lab actually measure?

Almost never the drug you took. A lab looks for whichever compound stays present longest and most reliably, and that is usually a metabolite. For cocaine that is benzoylecgonine. For ketamine it is ketamine together with norketamine. For amphetamine it is usually amphetamine itself, which is broken down relatively slowly.

That distinction is not academic. It sets the length of your window.

The compound chosen also sets the sensitivity. Researchers who measured benzoylecgonine with a more sensitive method and a lower cut-off found more positive results and longer half-lives than with traditional cut-offs (PMID 28024167). Same urine, same person, a different outcome, purely because of the threshold the lab applies.

What that threshold is exactly is explained in what a cut-off value is on a drug test. And why a positive screen should always be confirmed with a second technique is covered in screening versus confirmation.

How long do speed, ketamine, GHB and 3-MMC work?

In short: speed lasts longest of this group, GHB shortest. Amphetamine usually gives four to eight hours of effect, ketamine forty-five to ninety minutes, GHB around two to three hours and 3-MMC two to four hours. But the order of the detection windows is completely different, and that is the whole point.

In adults, amphetamine has an elimination half-life of roughly ten to twelve hours, peaking in blood after two to three hours (PMID 28910145). GHB, by contrast, has a half-life of twenty to sixty minutes and is largely out of the body within four to eight hours (PMID 22746383).

That makes GHB, of everything on a standard panel, by far the shortest window. A negative GHB result a few days later therefore tells you remarkably little.

Duration of effect next to detection window: the table

Below are both numbers side by side, with the compound the lab actually measures. The windows shown are for occasional use in urine. With regular or heavy use they stretch, sometimes considerably.

Being straight about the last two rows: Zuivertest does not test for cannabis (THC) and does not test for MDMA. They appear here purely for comparison, because people search for them and because they show how widely detection windows can diverge. We offer no test for either, and we would rather say so out loud than have you discover it at checkout.

Take two men who use the same amount of speed on a Saturday night and both give urine some 30 hours later. One comes out at 900 ng/ml, the other at 250 ng/ml, which leaves him under a common cut-off of 500 ng/ml. His result is called negative.

They used the same thing. Their kidneys simply did not.

That is exactly why a number on a result is not a dose. It is a concentration at a moment, driven by the acidity of your urine, your fluid intake and above all by the clock.

Why does the detection window vary so much per substance?

Four things drive that window: the half-life of the compound, its fat solubility, the way your kidneys excrete it, and the cut-off the lab applies. Change any one of those four and the window shifts, without you having done anything differently.

Fat solubility explains the outlier for cannabis. THC binds to fatty tissue and is released slowly, which is why it can take weeks in frequent users. GHB, by contrast, is highly water-soluble and is excreted very fast.

With amphetamine something else matters: the acidity of your urine. Amphetamine is a base, so acidic urine speeds up excretion while alkaline urine holds it back. Two people who used the same amount can end up with different windows.

That is precisely why you find such wildly different numbers online. They are often all correct, for somebody.

Does it matter whether you test urine, blood or hair?

Enormously. The same person, the same day, three different matrices and three different answers. Blood mostly shows what happened recently, urine looks back days, and hair looks back months. Which matrix you choose therefore decides which question you are actually asking.

Blood is the narrowest window, usually hours up to roughly a day. It comes closest to the moment itself, and it is the matrix that says most about current exposure.

Urine is the workhorse of almost every panel. Concentrations run higher than in blood, collection is non-invasive, and for most substances the window runs from a few days to well over a week with heavy use.

Hair is the long view. A hair analysis looks back roughly one month per centimetre, and with enough length you reach months into the past. What hair does not do is reliably pin down a single event from yesterday, because the substance first has to travel through the blood into the growing hair shaft.

Saliva sits somewhere in between, with a short window close to the moment of use.

So the choice is not about which test is best. It is about which period you want to cover. Which matrix suits which question is worked out in urine, saliva or hair test.

Why is a negative result not the same as "used nothing"?

Because a test only looks for what is on the panel, above a threshold, within a window. If any one of those three falls outside, you get a negative result even though something was used. That is not a lab error, it is the limit of what the measurement can see.

3-MMC is the clearest example. It is a designer cathinone, and a routine immunoassay is built around the classic substances. New psychoactive substances slip through as a matter of course unless the lab is explicitly asked to look for them. The Dutch national institute RIVM monitors these substances separately for exactly that reason, because they fall outside the beaten track of routine diagnostics.

With GHB it is the clock that works against you. Twelve hours later the party is over, for the lab too.

And the reverse holds as well: a positive result says there was exposure. It does not say how much you used, not exactly when, and certainly not whether you are dependent.

What does ng/ml mean on a result?

Nanograms per millilitre is the concentration of the measured compound in your urine. It is a measure of how much is still circulating at the moment the sample was taken, not of how much you used. The cut-off decides from which concentration a result is called positive.

If your value sits just below the cut-off, the result is called negative even though the substance is demonstrably present. Just above, and the same situation is called positive. The threshold is an agreement, not a law of nature.

That is why Zuivertest asks for quantified lab values rather than a stripe. A number you can track. A stripe you can only believe.

More on that in what ng/ml means on a drug test result.

What a lab value does and does not say about you

A lab value is a snapshot of exposure. It confirms whether a substance or its metabolite was present above the cut-off in the sample you provided. It claims nothing more, and you should not read more into it.

What it does not do: it does not diagnose, it does not measure addiction, it does not predict organ damage and it does not prove abstinence across a period in which no sample was taken. For symptoms that persist, your GP is the right person, not a test result. Thuisarts.nl and the Farmacotherapeutisch Kompas are useful Dutch starting points.

What it does do: it gives you a hard number instead of a suspicion. And at Zuivertest, only you see that number.

Which test fits which question?

It depends on what you want to know. For a broad picture across the classic substances, the Core 5-Panel drug screening is the logical starting point. To include the less common substances, GHB and 3-MMC among them, the Extended 10-Panel is the broader option.

If it is a single substance you care about, you do not need to pay for a whole panel.

We go deeper on each substance separately. Read what cocaine does to your body, from nose to heart, how long speed works and what amphetamine's side effects are, what ketamine does to your bladder, why the margin with GHB is so small, and what happens in the days after a 3-MMC comedown.

If you want the detection windows per substance without the pharmacology, how long drugs stay detectable is the overview you need.

I would start with the question behind the question. Someone who wants to know whether they are clean needs a number. Someone who wants to know what a substance is doing to their heart needs a cardiologist. A drug test answers the first question very well and the second not at all.

Every blood test result at Zuivertest includes a professional assessment by a BIG-registered doctor. Discuss your results with your GP before making treatment decisions.

Sources

• Jufer R.A. et al., "Elimination of cocaine and metabolites in plasma, saliva, and urine following repeated oral administration to human volunteers", Journal of Analytical Toxicology, 2000 (PMID 11043648)
• Nickley J. et al., "A sensitive assay for urinary cocaine metabolite benzoylecgonine shows more positive results and longer half-lives than those using traditional cut-offs", Drug Testing and Analysis, 2017 (PMID 28024167)
• Markowitz J.S. and Patrick K.S., "The Clinical Pharmacokinetics of Amphetamines Utilized in the Treatment of Attention-Deficit/Hyperactivity Disorder", Journal of Child and Adolescent Psychopharmacology, 2017 (PMID 28910145)
• Schep L.J. et al., "The clinical toxicology of gamma-hydroxybutyrate, gamma-butyrolactone and 1,4-butanediol", Clinical Toxicology, 2012 (PMID 22746383)
• Shimshoni J.A. et al., "3-Methyl-methcathinone: Pharmacokinetic profile evaluation in pigs in relation to pharmacodynamics", Journal of Psychopharmacology, 2015 (PMID 25804420)
• RIVM, monitoring and risk assessment of new psychoactive substances (rivm.nl)
• Farmacotherapeutisch Kompas, monographs on amphetamine and ketamine (farmacotherapeutischkompas.nl)
• Thuisarts.nl, information on drug use (thuisarts.nl)