A quantitative cotinine test measures the amount of cotinine — the main nicotine metabolite — in blood, saliva, or urine to objectively assess recent nicotine exposure. Results quantify exposure level, helping distinguish active smoking from secondhand exposure and monitor cessation or prenatal exposure. Cotinine’s half-life (about 16–20 hours) makes the test reliable for detecting tobacco use within several days; thresholds guide interpretation.

A qualitative cotinine test detects whether cotinine — the main nicotine metabolite — is present in urine, saliva, or blood, indicating recent tobacco use or exposure. Processing typically involves collecting a sample and running an immunoassay (rapid dipstick or lab ELISA) that yields a positive/negative result against a cutoff. Positive screens can be confirmed by quantitative methods (GC‑MS) for accuracy.

A positive cotinine test means nicotine exposure. It detects cotinine, a nicotine breakdown product, indicating recent use of cigarettes, e-cigarettes, nicotine replacement, or significant secondhand smoke. It doesn’t identify the exact source. Cotinine is usually detectable in blood, urine, or saliva for about 1–3 days (occasionally up to a week) and for months in hair; interpretation depends on timing and levels.

Cotinine results are reported in ng/mL. Typical cutoffs: serum/plasma <10 ng/mL suggests non‑smoker; 10–100 ng/mL may indicate passive exposure or light use; >100 ng/mL indicates active smoking. For urine, <50 ng/mL often denotes non‑exposure, 50–200 ng/mL passive exposure, >200 ng/mL active smoking. Interpret by specimen type, timing, nicotine replacement, and lab reference ranges; consult a clinician.

Stop all nicotine exposure — time is the main way to clear cotinine. Its half‑life is about 16–20 hours, so levels usually fall substantially within 3–4 days, though in heavy users it can take up to 2–3 weeks. Support clearance by staying well hydrated, exercising to boost metabolism, eating antioxidant‑rich foods, and resting. There’s no proven quick “detox”; consult a clinician for quitting help.

A commonly used urine cotinine cutoff to distinguish active smokers from nonsmokers is about 50 ng/mL. To reduce misclassification from secondhand exposure, some labs use higher thresholds (typically 100–200 ng/mL). Cutoffs vary by assay and purpose, so interpretation should consider testing method, timing, and clinical context. Cotinine is a stable nicotine metabolite with a roughly 16–20 hour half-life.