Testing information
What your results mean
A general framework for reading detected levels — and the reasons it is only a framework.
- Cutoffs by substance
- International alcohol bands
- Limits stated plainly
What was found is exact. When it happened is an estimate.
Which substances are in the hair, and how much of each, is measured to a very high degree of certainty. The laboratory uses mass spectrometry, which identifies a molecule by its mass rather than inferring it from a colour change or a reaction. A positive result is a positive result.
Dating that use is the approximate part. Hair does not all grow at the same speed — individual follicles grow at slightly different rates, and some are resting at any given time. It is the same reason a haircut never grows out perfectly evenly. So a length of hair corresponds to an approximate period, not to a particular day.
These are two separate questions, and this is the part worth being clear about: an estimated timeline does not make the substance finding any less reliable. The chemistry is precise. The calendar is approximate.
Reading a result
Read this before the tables.
Sorting people into low, medium and high from a concentration alone is an estimate, not a finding. Treating it as a finding is the most common error made with these results.
What a reliable reading needs alongside the number
- Context — self-reports, medical records, prescriptions.
- Individual factors — metabolism, hair pigmentation, and cosmetic treatment such as dyeing, bleaching or straightening.
- Confirmatory testing where warranted — segmental hair analysis, or a different sample type.
Accurate interpretation needs a qualified forensic toxicologist weighing these against the specific case. Dr Michael Robertson provides written interpretation reports.
How do I convert ng to pg?
Laboratories report hair results in either picograms or nanograms per milligram of hair. The same result looks very different depending on which is used. Every figure on this page is in pg/mg.
A picogram is one thousandth of a nanogram, so the conversion is just moving the decimal point three places:
- ng to pg — multiply by 1,000
- pg to ng — divide by 1,000
The same numbers, both ways
- 0.2 ng/mg = 200 pg/mg
- 1 ng/mg = 1,000 pg/mg
- 20 pg/mg = 0.02 ng/mg
Why this matters when comparing providers. A smaller-looking number is not a more sensitive test. A cutoff advertised as 0.2 ng/mg is the same thing as 200 pg/mg — which is ten times less sensitive than a 20 pg/mg cutoff, even though "0.2" reads as the smaller figure.
Levels by substance
Each substance below shows its low, medium and high concentration ranges, and what a result in each range generally indicates.
Opiates — Morphine
A metabolite of heroin
Occasional exposure. May also be present alongside codeine (codeine use) or 6-MAM (heroin use).
Repeat or multiple use occasions.
Regular use.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Occasional exposure. May also be present alongside codeine (codeine use) or 6-MAM (heroin use). |
| Medium | 200 – 3,000 pg/mg | Repeat or multiple use occasions. |
| High | > 3,000 pg/mg | Regular use. |
Cocaine
Infrequent recreational use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions.
Regular use.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 500 pg/mg | Infrequent recreational use, or incidental contamination where no metabolites are present. |
| Medium | 500 – 5,000 pg/mg | Repeat or multiple use occasions. |
| High | > 5,000 pg/mg | Regular use. |
Amphetamine
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 2,500 – 7,500 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 7,500 pg/mg | Regular use, recreational or prescribed. |
Methylamphetamine
Infrequent recreational use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions.
Regular use.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Infrequent recreational use, or incidental contamination where no metabolites are present. |
| Medium | 2,500 – 7,500 pg/mg | Repeat or multiple use occasions. |
| High | > 7,500 pg/mg | Regular use. |
MDMA
Infrequent recreational use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions.
Regular use.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Infrequent recreational use, or incidental contamination where no metabolites are present. |
| Medium | 500 – 7,500 pg/mg | Repeat or multiple use occasions. |
| High | > 7,500 pg/mg | Regular use. |
Ketamine
Infrequent recreational use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions.
Regular use.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Infrequent recreational use, or incidental contamination where no metabolites are present. |
| Medium | 200 – 2,000 pg/mg | Repeat or multiple use occasions. |
| High | > 2,000 pg/mg | Regular use. |
THC
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 1 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 1 – 10 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 10 pg/mg | Regular use, recreational or prescribed. |
Carboxy-THC
The metabolite that distinguishes ingestion from external contact
Infrequent THC use, recreational or prescribed.
Repeat or multiple THC use occasions, recreational or prescribed.
Regular THC use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 0.1 pg/mg | Infrequent THC use, recreational or prescribed. |
| Medium | 0.25 – 1.0 pg/mg | Repeat or multiple THC use occasions, recreational or prescribed. |
| High | > 5 pg/mg | Regular THC use, recreational or prescribed. |
Synthetic cannabinoids
Limited published literature; concentrations are likely similar to THC
Limited literature. Likely similar to THC.
Limited literature. Likely similar to THC.
Limited literature. Likely similar to THC.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 1 pg/mg | Limited literature. Likely similar to THC. |
| Medium | 1 – 10 pg/mg | Limited literature. Likely similar to THC. |
| High | > 10 pg/mg | Limited literature. Likely similar to THC. |
Cannabidiol (CBD)
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 50 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 50 – 1,000 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 1,000 pg/mg | Regular use, recreational or prescribed. |
Fentanyl
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 10 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 10 – 100 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 100 pg/mg | Regular use, recreational or prescribed. |
Oxycodone
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 100 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 100 – 2,000 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 2,000 pg/mg | Regular use, recreational or prescribed. |
Diazepam (Valium)
Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present.
Repeat or multiple use occasions, recreational or prescribed.
Regular use, recreational or prescribed.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Infrequent recreational or prescribed use, or incidental contamination where no metabolites are present. |
| Medium | 200 – 1,000 pg/mg | Repeat or multiple use occasions, recreational or prescribed. |
| High | > 1,000 pg/mg | Regular use, recreational or prescribed. |
Codeine
Occasional exposure. May also be present alongside morphine.
Repeat or multiple use occasions, recreational or prescribed. May also be present alongside morphine.
Regular use, recreational or prescribed. May also be present alongside morphine.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 200 pg/mg | Occasional exposure. May also be present alongside morphine. |
| Medium | 200 – 3,000 pg/mg | Repeat or multiple use occasions, recreational or prescribed. May also be present alongside morphine. |
| High | > 3,000 pg/mg | Regular use, recreational or prescribed. May also be present alongside morphine. |
Steroids
Many of these compounds are produced naturally, so presence alone means little
Typically within the low physiological range. May reflect low endogenous production or no external exposure.
Typically seen in healthy adults, particularly males, though this varies by the specific steroid. Cortisol in healthy individuals has been reported between 1–20 pg/mg; testosterone in males commonly falls in the 5–15 pg/mg range. Age, sex, BMI, hair colour, treatment history, stress and metabolism all affect the figure.
Suggestive of elevated exposure — high endogenous output, supplementation, or external application. There is no direct correlation between dose and hair concentration.
| Level | Concentration | Indicates |
|---|---|---|
| Low | < 2 pg/mg | Typically within the low physiological range. May reflect low endogenous production or no external exposure. |
| Medium | 5 – 15 pg/mg | Typically seen in healthy adults, particularly males, though this varies by the specific steroid. Cortisol in healthy individuals has been reported between 1–20 pg/mg; testosterone in males commonly falls in the 5–15 pg/mg range. Age, sex, BMI, hair colour, treatment history, stress and metabolism all affect the figure. |
| High | > 20 pg/mg | Suggestive of elevated exposure — high endogenous output, supplementation, or external application. There is no direct correlation between dose and hair concentration. |
EtG (alcohol)
Bands set by international consensus
No significant alcohol use; not inconsistent with abstinence. May reflect incidental or environmental exposure.
Moderate consumption, such as regular social drinking.
Heavy or chronic use, indicative of frequent consumption.
| Finding | Concentration | Indicates |
|---|---|---|
| Abstinent or very irregular consumption | < 5 pg/mg | No significant alcohol use; not inconsistent with abstinence. May reflect incidental or environmental exposure. |
| Regular consumption | 5 – 30 pg/mg | Moderate consumption, such as regular social drinking. |
| Chronic excessive consumption | > 30 pg/mg | Heavy or chronic use, indicative of frequent consumption. |
Why low / medium / high has limits
Eight reasons a concentration alone can mislead. These are the arguments run against hair evidence in court — worth understanding whichever side you are on.
1. Biological variability
- Hair growth rates differ between people. Faster growth dilutes concentration; slower growth concentrates it over the same period.
- Hair type and colour matter. Darker, more porous hair incorporates more drug, which can skew a result upward.
2. Environmental contamination
- Passive exposure — second-hand smoke, handling a substance — can produce detectable levels without ingestion.
- Drugs can adhere to the outside of the hair, particularly in environments where they are present.
3. Inconsistent incorporation
- Lipophilic drugs such as THC accumulate more readily than hydrophilic ones, so the same usage produces different concentrations across substances.
- Individual metabolic rates change how much of a substance reaches the hair at all.
4. Limits of sensitivity
- Where a laboratory sets its cut-off determines whether infrequent use registers at all.
- Distinguishing 'low' from 'medium' with precision is difficult for sporadic use.
5. Timeline ambiguity
- Without segmenting the sample, a single result averages months and hides periods of heavy or light use.
- A chronic user who recently stopped may still be classified as 'high'.
6. Polydrug use
- One substance may sit at 'high' while another sits at 'low', which makes a single overall classification meaningless.
7. No contextual information
- Hair analysis cannot distinguish intentional use from a prescription or accidental ingestion.
- It measures deposition, not how frequently or in what quantity a substance was consumed.
8. Legal and ethical concerns
- Simplistic categories invite unfair assumptions in legal and employment contexts.
- Courts may question a categorisation based on hair testing alone, given the variability above.
Need your results interpreted?
Dr Michael Robertson gives verbal opinions and written reports on results from any source — hair, blood, urine, saliva or breath.