This is not a laboratory study. It is a single-person log: cannabis smoked once on the evening of Wednesday 28 October 2026, then eight shop-bought THC urine dip tests over the next two days, each photographed against a clock screen so the time and date are visible in the frame.

We are publishing it because readers ask the same question in different words: *If I smoke once, how long am I “hot” on a piss test?* Textbooks give a range. This piece adds what that range looked like on home kits for one occasional user — with timestamps attached.

Session: Wednesday 28 October 2026, about 21:00 — one smoke, usual hydration, no second use logged during the test window.

Tests: retail THC urine cassettes (50 ng/mL class cut-off, typical of UK workplace panels). Read rule on the packet: two lines (control C + test T, even a faint T) = negative; control line only = positive.

How the tester read them: positive on every run except the last — only the Friday 19:08 card was called negative. Some photos show a ghost-thin T band on earlier runs; the person logging the test still treated those as positive (control-only reads, or T too faint to trust). The diary entries below are that field interpretation; each has a matching photo with the clock visible in frame.

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The diary

Wednesday 28 October — session

~21:00. One smoke. No further use logged during the test window. Starting the clock here.

Thursday 29 October, 11:16 (~14 hours after smoking)

Result: positive. First dip test in the series — already C only, no T line the tester was willing to call. Roughly half a day after a single evening session, the metabolite window on this kit was already open.

Thursday 29 October, 13:15 (~16 hours)

Result: positive. Control line only again. Same day, second read; still clearly above the kit’s cut-off on a field read.

Thursday 29 October, 15:15 (~18 hours)

Result: positive. Still positive mid-afternoon. The photo may show the faintest shadow at T; it was not treated as a negative.

Thursday 29 October, 16:46 (~20 hours)

Result: positive. Unambiguous C-only read on the cassette in frame.

Thursday 29 October, 23:16 (~26 hours)

Result: positive. Late evening, still positive — a full day after smoking and the dip test had not cleared.

Friday 30 October, 08:13 (~35 hours)

Result: positive. First test next morning, still C only on the tester’s read. Metabolites in urine often peak and plateau; this log did not “flip” overnight.

Friday 30 October, 12:19 (~39 hours)

Result: positive. Midday Friday, seventh run — still positive on the same interpretation rules.

Friday 30 October, 19:08 (~46 hours)

Result: negative. First clear C + T in the series. About 46 hours after the Wednesday 21:00 smoke on these home kits. Insert the final photo here in the published piece.

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What this single log suggests

1. One evening smoke was enough to stay “hot” on dip tests for roughly two days. From 21:00 Wednesday to the first negative at 19:08 Friday is about 46 hours on this person’s kits. That sits inside the one-to-three-day window often quoted for occasional use on 50 ng/mL urine screens — but this n=1 log is not a guarantee for you, your dose, or your metabolism.

2. The first test in the series was already positive. The 11:16 Thursday entry (~14 hours after smoking) was still positive. Parent THC in the blood falls within hours; THC-COOH in urine rises and stays elevated longer — so a positive dip test the morning after a single session is expected, not exceptional.

3. Home kits are coarse instruments. Faint T lines, hydration, and timing within the five-minute read window can split people on whether a run is “weak negative” or “still positive.” We report the tester’s calls in the diary above; a lab confirmation on the same samples could disagree.

4. Smoking vs vaping does not change the metabolite. Combustion adds smoke chemistry; it does not bypass THC-COOH in urine. Roadside saliva kits mostly look for recent THC, not the same metabolite pool — see below.

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Urine vs saliva: what each test actually sees

Urine dip tests (this case study)

These kits target THC-COOH, the main urine metabolite, usually at a 50 ng/mL-class screening cut-off. For occasional use, passing a standard panel is often quoted at roughly one to three days; daily or heavy use can run to weeks. What they show is recent metabolism of cannabis — not whether someone is impaired at the moment of the test. In the UK they appear in workplace pre-employment screens and some probation or medical programmes.

Saliva (oral fluid) tests

Saliva kits look mainly for THC itself — the parent drug in the mouth and blood — not the same metabolite pool as urine. The detection window for a single session is typically shorter: often about six to 24 hours, with some roadside devices quoting up to 48 hours. They answer a different question: recent exposure, not “have you processed cannabis over the last few days?” UK police roadside screening and some on-site workplace swabs use this route.

Saliva can go negative while urine is still positive — common after one session because mouth levels fall while urine metabolites linger. Do not assume a clear mouth swab means a clear lab urine panel.

Neither home dip cards nor this article constitute legal advice. Workplace policies, confirmatory GC-MS at the lab, and medical cannabis prescriptions each change what counts as a “fail.”

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How we logged it (so you can replicate or challenge it)

- Same brand of cassette where possible; each photo shows the device lock-screen time in frame. - Results read at the manufacturer’s stated wait time (typically 3–5 minutes). - No adulterants or deliberate dilution — interest was clearance time, not evasion. - Limitations: n=1; unknown potency and amount smoked; no lab confirmation; dip tests are screening tools; clock is a consumer device, not a certified timestamp.

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The home test kit (AYDMED 10-pack)

Every urine dip in this diary came from one retail box: AYDMED Cannabis Drug Tests (10 pack) — 50 ng/mL THC screening cassettes with the usual C / T legend on each strip.

We published a standalone product review covering how they performed across this log, plus pros, cons, and what screening-grade dips can and cannot tell you. If you buy the same kit, our Amazon link supports the site at no extra cost to you.

Practical takeaways for UK readers

- One social smoke on Wednesday evening kept these dip tests positive through Friday lunchtime and only cleared on the Friday evening read (~46 hours). - Plan in days, not hours, if you face a real workplace or legal urine screen — home kits are a rough guide only. - Saliva and urine answer different questions and on different clocks. - For legal dry-herb use (where permitted), device choice is separate from clearance; our dry-herb vaporiser reviews compare hardware — metabolite rules are the same once THC is absorbed.

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Sources & further reading

- SAMHSA / DHHS guidelines on urine cut-offs (THC-COOH 50 ng/mL screening) — US reference used by many UK lab contracts. - Verstraete, *Analysis of Drugs of Abuse in Saliva* — parent THC vs metabolites in oral fluid (overview). - Huestis, *Human Cannabinoid Pharmacokinetics*, *Chemical & Biodiversity* — absorption, metabolism and elimination after smoking and vapourisation. - Doubling THC dose does not double the high — dose and clearance both vary non-linearly with habit and amount.

Editorial note: Cannabis remains controlled outside licensed medical routes in the UK. This case study describes personal logging with legally possessed material in the tester’s jurisdiction at the time of writing; readers remain responsible for their own compliance with local law.