How long do drugs and alcohol stay in your system
How long a substance remains detectable depends on the drug, how it was used, and which sample is tested. This guide explains the detection window for each sample type, with a substance-by-substance summary and the factors that shift it.
The short answer
Detection windows by sample type
Different samples answer different questions. Urine and oral fluid tell you about recent use; hair and nail testing reveal a pattern over months. There is no single "how long" — it depends on what is being tested and why.
| Sample | Typical detection window | Best for |
|---|---|---|
| Oral fluid (saliva) | Typically 1 to 2 days; cannabis in frequent users can be detected for longer | Very recent use; observed, rapid collection |
| Urine | Most drugs a few days (typically 1–5); cannabis longer with frequent use | Recent use over the past few days |
| Hair | Approximately 1 month per cm; a 3 cm segment ≈ 3 months | Patterns of use over months; supporting a statement of abstinence |
| Nail | Fingernails around 3 to 6 months; toenails longer | Long-term history where hair is unavailable |
| Blood | Short for most drugs; PEth reflects roughly the previous 2 to 4 weeks for alcohol, and longer after heavy drinking | Near-term alcohol markers alongside hair |
This page is a general guide. It is not legal, medical or technical advice. Laws, guidance and laboratory methods change, so check the current requirements for your own case. Detection windows are indicative. They vary with the substance, dose, how often it is used and the individual. Last reviewed .
Detection windows by substance
Select a substance to see how long it is typically detectable in each sample. These figures are NIVHA's own indicative estimates — an approximate estimate of drug presence, not a fixed limit.
Drugs
Alcohol markers
Direct markers (EtG, EtS, PEth) have dated windows. CDT and liver function tests are chronic markers — they reflect a sustained pattern of heavy drinking over weeks, not a countdown from the last drink.
The hair testing "lag phase"
Hair testing has one important quirk: it does not reflect the last few days. Drugs and their metabolites are laid down in the hair as it grows, and it takes time for that newly grown hair to emerge above the scalp where it can be sampled. Allow roughly one to two weeks from use.
What shifts the window
The figures above are typical ranges, not fixed limits. Several factors move them:
- Dose and frequency. Heavier, more frequent use is detectable for longer — most markedly with cannabis, which is stored in body fat.
- Individual metabolism. Body composition, hydration, kidney and liver function all affect how quickly a substance clears.
- The substance itself. Different drugs clear at very different rates, and some produce metabolites that persist after the parent drug has gone.
- Sample condition. For hair, cosmetic treatments such as bleaching can affect some markers — always disclose them so the laboratory can interpret the result correctly.
Screening versus confirmation
An initial screen indicates whether a substance may be present. Any non-negative screen is then confirmed at an accredited laboratory by a more specific method. It is the confirmation step, not the screen, that identifies exactly which substance is present. Understanding your result explains cut-offs and what positive and negative actually mean.
Choosing the right test
Because each sample answers a different question, the right choice depends on your objective:
- Recent use — oral fluid or urine, with laboratory confirmation of any non-negative screen. Common in workplace testing for unannounced, for-cause and post-incident situations.
- A pattern over months — hair testing, segmented where a timeline matters. Common in court and safeguarding cases.
- Both — many cases instruct hair together with urine, evidencing recent use and a longer-term pattern in a single instruction.
For a full comparison of every sample type, see choosing the right sample.
Common questions
Detection windows — your questions answered
How long does alcohol stay in your system?
A breath or blood test detects alcohol only while it is still being cleared — typically a matter of hours, at an average elimination of roughly one unit per hour. To evidence longer-term drinking, hair testing (EtG and FAEE markers) reflects consumption over months, and the blood marker PEth reflects roughly the previous two to four weeks, and longer after heavy drinking. The right test depends on whether the question is recent use or a sustained pattern.
How long does cannabis stay in your system?
In urine, occasional cannabis use is usually detectable for a few days, but frequent or heavy use can remain detectable for considerably longer because it is stored in body fat and released over time. Oral fluid reflects more recent use — typically one to two days, and longer in frequent cannabis users. Hair testing can show a pattern of use over months.
Which test looks back the furthest?
Hair and nail testing look back the furthest. A 3 cm scalp hair sample reflects roughly the previous three months, and longer hair can be segmented for a month-by-month picture. Fingernails reflect around three to six months of history; toenails look back further. Urine and oral fluid answer questions about recent use, not long-term patterns.
Can I speed up how quickly a drug leaves my system?
No reliable method removes drugs from the body faster, and attempts to dilute or adulterate a sample can often be identified. Accredited testing includes validity checks for dilution and tampering.
Not sure which test you need?
Tell us what the result needs to show and we will recommend the right sample and testing approach — for a court case, a workplace programme or a private matter.