What this test measures
Nicotine itself has a short half-life (1–2 hours) and is rarely measured directly. The body converts most nicotine to cotinine (half-life ~16 hours) and then to trans-3'-hydroxycotinine (3HC). The ratio 3HC / cotinine is the "Nicotine Metabolism Ratio" — a marker of CYP2A6 activity and an emerging predictor of smoking cessation success (slower metabolisers benefit more from nicotine replacement therapy).
Why it matters
In India this combined panel is used for the same indications as cotinine — pre-transplant / bariatric evaluation, insurance, return-to-work, cessation programmes — but with better sensitivity for very-recent exposure (catches occasional use the day before) and added research utility. Some commercial panels add anatabine and nornicotine to distinguish smoked tobacco from pure NRT.
How to prepare
Random urine; no fasting required. Disclose nicotine replacement (gum, patches, vapes), chewing tobacco use, and any household second-hand smoke exposure.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Urine Cotinine (ng/mL)[1] | Non-user: < 6; Passive: 6 – 50; Active: > 50 | < 6 — no recent nicotine. | > 50 — active recent exposure (smoking, NRT, smokeless). |
| trans-3'-hydroxycotinine (3HC) (ng/mL)[1] | Typically 0.1 – 3.0× cotinine in active users | Very low 3HC with detectable cotinine → slow CYP2A6 metaboliser. | High 3HC:cotinine ratio → fast metaboliser; predicts harder cessation, may need higher-dose NRT or varenicline. |
Nicotine metabolism ratio (3HC / Cotinine)
| 3HC : Cotinine | Metaboliser type | Implication |
|---|---|---|
| < 0.31 | Slow | NRT works well; lower dose often sufficient |
| 0.31 – 0.55 | Intermediate | Standard NRT dose |
| > 0.55 | Fast | Higher cessation difficulty; consider varenicline or higher NRT dose |
Frequently asked questions
How is this different from a simple cotinine test?
It adds trans-3'-hydroxycotinine, the next metabolite, allowing the nicotine metabolism ratio to be calculated — useful in cessation planning and research.
Will NRT show positive?
Yes — all nicotine sources (smoke, vape, gum, patch, gutka) produce cotinine and 3HC.
Why is the ratio clinically useful?
Fast metabolisers clear nicotine quickly and feel withdrawal sooner — they tend to relapse more on standard NRT and may benefit from varenicline. Slow metabolisers respond better to NRT.
How long after quitting do values normalise?
Cotinine and 3HC both fall below detection thresholds 5–10 days after complete cessation in most users.
Can second-hand smoke push my result into the active range?
Rarely — second-hand exposure usually keeps urine cotinine well under 50 ng/mL.
Related Toxicology / Trace Elements tests
Tests commonly ordered alongside NICOTINE METABOLITES, or that help interpret an unexpected result.
Sources & references
- CDC — Cotinine Biomonitoring · accessed 2026-05-30T00:00:00.000Z
- SRNT — Biomarkers of Tobacco Exposure · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Nicotine and Metabolites · accessed 2026-05-30T00:00:00.000Z
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