How long a drug can be detected depends above all on the sample: in saliva and blood usually for hours or at most a few days, in urine for days (with regular cannabis use even for weeks), and in hair for months. From a legal point of view it matters just as much what is detected: an inactive breakdown product that only shows past use, or an active substance still present in the blood. The figures below are ranges from the scientific literature; dose, frequency of use, body weight, metabolism and the sensitivity of the test method can change them considerably from person to person.
By Dr. László-Tamás Benő and Dr. Ildikó Willi, criminal defence lawyers
Half-life and detectability are not the same
The half-life is the time it takes for the concentration of a substance in the blood to fall by half; after four to five half-lives most of the active substance has been eliminated. Detectability means that a laboratory can still find the substance or its breakdown product (metabolite) above a given cut-off. Many metabolites stay in the body far longer than the drug itself: THC becomes THC-COOH, cocaine becomes benzoylecgonine. A metabolite can prove earlier use, but on its own it does not prove impairment at the time of the alleged offence.
Effects and half-lives of the main drugs
Cannabis (THC). Can cause euphoria, relaxation, distorted perception of time and space, slower reactions and impaired attention. After smoking, blood THC peaks within minutes and then falls quickly, usually to low levels within two hours. THC is stored in fatty tissue, so in regular users its terminal half-life can be several days. The plasma half-life of the inactive metabolite THC-COOH averages about 5–6 days in studies.
Cocaine. Short, intense stimulant effect: heightened alertness and confidence, rapid heartbeat, raised blood pressure, followed by a low mood. The plasma half-life of cocaine is about 1–1.5 hours; that of its main metabolite, benzoylecgonine, about 6–7 hours, and benzoylecgonine is eliminated from urine more slowly.
Amphetamine, methamphetamine. Longer stimulant effect, reduced need for sleep and appetite, restlessness; at higher doses anxiety and paranoid thoughts may occur. The half-life of amphetamine is usually around 10–14 hours, methamphetamine is of a similar order; elimination is strongly affected by urine pH.
MDMA (ecstasy). Stimulant effect with increased feelings of closeness, raised body temperature, jaw tension, followed by low mood for days. Its half-life is about 7–11 hours; some metabolites (e.g. MDA) remain longer.
Heroin and other opiates. Pain relief, sedation, narrow pupils, slow breathing; risk of respiratory arrest in overdose. Heroin has a half-life of only a few minutes; it is converted first to 6-monoacetylmorphine (6-MAM) and then to morphine. 6-MAM is a specific marker of heroin but is found in urine only for a few hours.
Benzodiazepines. Anti-anxiety, sedative and sleeping medicines; they can cause drowsiness, slow reactions and poor coordination, with stronger effects when combined with alcohol. Half-lives vary widely: according to its label diazepam can have a half-life of up to 48 hours and its active metabolite (nordiazepam) up to 100 hours, while short-acting drugs have half-lives of a few hours. A prescribed medicine can also be a “substance impairing the ability to drive”.
New psychoactive substances (synthetic cannabinoids, cathinones). The effects of synthetic cannabinoids are unpredictable and often much stronger than those of cannabis; cathinones (e.g. mephedrone) are stimulants. Reliable data on their half-lives and detection times are limited because the compounds keep changing. Standard rapid tests do not detect many new compounds at all; targeted laboratory analysis (mass spectrometry) is needed.
Detection times by sample type
Indicative ranges for single or occasional use; with regular use they can be longer.
| Drug | Saliva | Blood | Urine | Hair |
|---|---|---|---|---|
| Cannabis (THC / THC-COOH) | THC usually up to 1 day, up to 1.5 days | active THC usually from a few hours up to about 1 day; THC-COOH up to weeks | THC-COOH usually 1–3 days for occasional users, about 10 days for daily users, 30 days or more with long-term heavy use | months |
| Cocaine (benzoylecgonine) | cocaine about 5–12 hours, benzoylecgonine about 1 day | cocaine a few hours; benzoylecgonine up to 2 days | benzoylecgonine usually 2–4 days, up to 1 week; longer with long-term use | months |
| Amphetamine, methamphetamine | about 1–2 days | about 1–2 days | usually 1–3 days | months |
| MDMA | limited data | about 1 day | usually 1–3 days | months |
| Heroin / opiates | 6-MAM a few hours; morphine about 1 day | morphine about 1 day | 6-MAM a few hours; morphine usually 2–3 days | months |
| Benzodiazepines | varies, limited data | from a few hours to several days | about 2 days for short-acting drugs, up to 10 days for long-acting ones (e.g. diazepam) | months |
| New psychoactive substances | limited data | usually short | depends on the compound, only with targeted testing | with targeted testing |
Head hair grows on average about 1 cm a month, so a 3 cm segment close to the scalp covers roughly the last 3 months. Hair testing is suited to showing long-term or repeated use; it cannot date an event of a few days and external contamination may affect the result.
How is testing done in Hungary?
- Roadside saliva rapid test. During traffic checks the police may use a rapid test on a saliva sample. This is only a screening test: it is indicative and drugged driving cannot be established on its result alone.
- Blood and urine samples. After a positive rapid test or on suspicion, medical staff take blood and urine samples into a standard sampling kit, with a record that also notes clinical symptoms.
- Forensic toxicology. The laboratory identifies and measures the substances with a confirmatory method (chromatography, mass spectrometry). This is the evidence, not the rapid test.
- Forensic medical expert opinion. A forensic medical expert gives an opinion on whether the driver was under the influence, based on the toxicology result, the time of sampling and the case file.
- Hair testing. Used mainly in special situations (e.g. the question of long-term use), not typical in traffic cases.
Why this matters legally
Drug-driving (Section 237 of the Hungarian Criminal Code). The law punishes driving “under the influence of a substance impairing the ability to drive” and, unlike for alcohol, sets no numerical limit. In practice it is close to zero tolerance: if the active substance in a blood sample taken within a few hours of the incident reaches the value set in the forensic guidance, impairment can be established even without visible symptoms or driving errors. Detecting only an inactive breakdown product (e.g. THC-COOH), however, only shows that use took place earlier; on its own it does not prove drugged driving. That is why it is decisive what exactly was measured, in which sample and when. More: Drug-driving in Hungary – defence lawyer. On alcohol: How long does alcohol stay in your body?
Drug use and possession. In Hungary drug use itself is a criminal offence, so a positive urine or blood test can be the basis of drug proceedings even if nothing was found on the person. Because of the longer detection window, a sample often reflects use days earlier, which can be significant for establishing when and where the offence took place. More: Drug offences in Hungary – defence lawyer.
What to do if a sample is taken from you
- Do not make detailed statements about when or how much you used before speaking to a lawyer; as a suspect you have the right to remain silent.
- Do not obstruct the sampling: refusing it may have separate legal consequences and does not help the defence.
- Note the times: when you were stopped and when blood was taken. The time between the incident and sampling is key to the expert assessment.
- Tell the officers if you take prescribed medication and be ready to prove it later.
- Ask for a copy of the record and check with your lawyer whether a control sample suitable for re-testing was kept.
- The expert opinion can be challenged: the defence can put questions to the expert and obtain a private expert opinion, for example on the lawfulness of the sampling, whether the measured substance was active or inactive, or how the elapsed time was assessed.
How criminal proceedings work: Criminal proceedings in Hungary – stages, questions and answers.
Frequently asked questions
If the rapid test was positive, will I definitely be convicted? No. The rapid test is only a screening; the evidence is the laboratory analysis and the forensic medical opinion. Rapid tests can also give false results.
I used a few days ago but felt no effect while driving. Is that drug-driving? What matters is whether an active substance was present in the blood that can be related back to the time of driving. If only an inactive breakdown product was found, that alone does not prove drug-driving, although proceedings for drug use may still be started.
Can passive cannabis smoke cause a positive result? In a small, closed space low values are theoretically possible, but the cut-offs of confirmatory testing largely exclude this. Such a defence can only be raised on an expert basis, case by case.
Can a medicine make me “under the influence”? Yes, the law is not limited to illegal drugs. In such cases the expert also considers the therapeutic dose and whether the drug was prescribed.
Can I see what the expert opinion says? Yes, the suspect and the defence lawyer can see the opinion and comment on it.
Sources
- Huestis, M. A.: Pharmacokinetics and Metabolism of the Plant Cannabinoids. Handbook of Experimental Pharmacology 168 (2005)
- Jufer, R. A. et al.: Elimination of Cocaine and Metabolites in Plasma, Saliva, and Urine. Journal of Analytical Toxicology 24 (2000)
- Verstraete, A. G.: Detection times of drugs in blood, urine, oral fluid and hair. Annales de Toxicologie Analytique XIV/4 (2002)
- Mayo Clinic Laboratories, Drug Book: Marijuana, Cocaine, Amphetamine-type stimulants, Opiates, Benzodiazepines
- Adderall (amphetamine) prescribing information, FDA; Diazepam label (DailyMed)
- de la Torre, R. et al.: Pharmacology of MDMA in humans. Ann N Y Acad Sci 914 (2000)
- Society of Hair Testing: General Consensus on Hair Testing (2022)
- Franz, F. et al.: Screening for synthetic cannabinoids in urine by immunoassay versus LC-MS/MS (EAFS 2015)
- Kovács, G. et al.: Methodological recommendation on forensic medical opinions in drug-driving cases. Belügyi Szemle 2023/7 (in Hungarian)
- Hungarian Criminal Code (Act C of 2012), Section 237; Act XIX of 2025 (National Legislation Database, in Hungarian)
About the authors: Dr. László-Tamás Benő has worked as a criminal defence lawyer since 2002 and has represented clients in more than 4,000 criminal cases, particularly in drug offences and driving under the influence; available day and night: +36 70 379 0245. Dr. Ildikó Willi has practised as a lawyer since 2003 and has represented clients in more than 3,600 criminal cases, particularly in drug offences and driving under the influence; available day and night: +36 20 987 6967. Contact →
This article is general information and does not constitute legal or medical advice.