Source-backed half-life profile
Caffeine half-life calculator
Caffeine is the everyday example that makes half-life feel real: a familiar dose can still leave a meaningful modeled tail long after the obvious lift has faded.
Every curve begins at 100%. No dose or measured body concentration is assumed.
X-axis: elapsed time. Y-axis: modeled percentage of the relative starting point remaining. The shaded band shows the reported half-life range. This is a mathematical visualization, not a personal concentration estimate.
What a careful reader should notice first
This page is best read as a sleep-and-timing literacy tool, not as a promise about alertness. The curve helps explain why a morning, afternoon, or evening exposure can feel different even when the starting amount looks ordinary.
Source angle
The source mix pairs a clinical pharmacology overview with labeling and compound identity records, so the useful reading move is to look for variability rather than a single universal coffee number.
Do not use it for
Do not use the remaining percentage as a sleep-quality forecast. Sensitivity, tolerance, pregnancy status, smoking status, liver metabolism, and co-medications can all change the practical story.
Best next step
Compare it with nicotine, modafinil, and amphetamine to see how stimulant curves can feel familiar while behaving very differently.
Caffeine: evidence and interpretation notes
Five hours is a useful center, not a coffee rule
The NCBI Bookshelf pharmacology chapter reports a mean plasma half-life of about five hours in healthy people, with a much broader 1.5-to-9.5-hour range. HalfLifeDB uses the mean because it makes the arithmetic easy to inspect: after five modeled hours, 50% remains; after ten, 25% remains. The range band is the more honest part of the picture because two people can sit at very different points within it.
The chapter describes caffeine as rapidly absorbed and largely metabolized rather than excreted unchanged. Its primary metabolic pathway involves CYP1A2, with paraxanthine as the dominant metabolite. Those details help explain why a caffeine curve is not simply a measure of how quickly liquid coffee leaves the stomach.
| Evidence source | What it contributes | Important limit |
|---|---|---|
| NCBI Bookshelf pharmacology chapter | Five-hour mean, reported range, absorption, first-order behavior, and metabolism | It summarizes many studies and populations rather than one contemporary cohort |
| DailyMed caffeine labeling | A medically described oral-product context | A product label is not a study of every beverage, serving pattern, or consumer |
| PubChem identity record | Compound identity and chemistry | It is not the evidence used to choose the five-hour value |
Why individual curves move apart
The chapter identifies physiological and environmental factors that change caffeine clearance, including pregnancy, oral contraceptive use, smoking, and liver-related metabolism. Smoking tends to increase clearance through enzyme induction; pregnancy can substantially prolong elimination. Genetic differences in CYP1A2 activity and interacting medicines can add more variation.
These are not minor exceptions to be hidden below a universal number. They are the reason the profile presents both a center value and a range. HalfLifeDB does not ask visitors to enter pregnancy status, smoking status, medicines, or genetic information because a public calculator cannot safely convert those details into an individualized estimate.
Persistence is not the same as feeling alert
A modeled remainder can help explain why caffeine consumed earlier may still be present later. It cannot forecast whether someone will sleep well, feel anxious, notice stimulation, or experience cardiovascular effects. Tolerance and sensitivity can change the perceived response even when the mathematical curve is unchanged.
The practical reading is limited but useful: five hours is a defensible educational average, the credible range is wide, and the percentage remaining should be treated as a visualization of pharmacokinetic persistence rather than a sleep recommendation.
Reading this curve
HalfLifeDB uses 5 h as a representative input for Caffeine. In the simplified model, about 3.6% remains after 24 hours and about 3% remains after five half-lives, or roughly 25 h.
This sits in the same-day range. The chart is useful for seeing the bend of the curve across a day or two, but it should not be treated as a personal clock. The curve is relative: it does not estimate a person's measured concentration, effects, impairment, or time to clearance.
stimulant context
Stimulant half-life estimates can shift with urine pH, enzyme activity, formulation, dose, and whether metabolites are measured separately.
- Alertness or subjective stimulation can end before modeled elimination.
- Sleep disruption and downstream effects are not represented by the curve.
- Formulation and route can change peak timing without changing the displayed model.
Caffeine timeline checkpoints
| Elapsed time | Modeled remaining | Reading note |
|---|---|---|
| 6 h | 43.5% | Meaningful modeled decline, not near-zero |
| 12 h | 18.9% | Long-tail portion of the model |
| 24 h | 3.59% | Low modeled remainder, not a clearance guarantee |
| 2.0 days | 0.13% | Low modeled remainder, not a clearance guarantee |
| 3.0 days | 0.00% | Low modeled remainder, not a clearance guarantee |
Nearby profiles by half-life
These entries sit near Caffeine within the stimulant group when sorted by representative half-life. That makes them curve comparisons, not statements about equal potency, effects, or risk.
Pharmacokinetics at a glance
| Representative half-life | 5 h |
|---|---|
| Reported range | 1.5 h to 9.5 h |
| Curve type | Normalized, first-order decline |
Selection note: The linked NCBI Bookshelf chapter reports a mean plasma half-life of about 5 hours in healthy people and a 1.5-to-9.5-hour range.
Sources and evidence context
A linked record is not automatically proof of the displayed value. Study, labeling, review, and compound identity sources serve different purposes; notes below identify limitations when they are known.
- Clinical reference Bonati M. Pharmacology of caffeine. NCBI Bookshelf.Clinical pharmacology chapter supporting the five-hour mean, 1.5-to-9.5-hour range, first-order model, and major sources of variability.
- Official labeling DailyMed label: Caffeine tablet.Official product information included for formulation context, not as the sole source for the displayed range.
- Identity record PubChem Compound Summary: Caffeine.Compound identity record; background only, not independent numerical support.
What this page does not answer
- It does not estimate impairment, intoxication, or fitness to drive.
- It does not predict urine, blood, saliva, or hair test results.
- It does not model repeated exposure, tolerance, withdrawal, or interactions.
- It does not replace clinician, pharmacist, toxicologist, or emergency guidance.
Continue with context
- All substance profiles
- Browse the stimulant group
- Compare this curve
- Clearance and volume of distribution
- Bioavailability, route, and formulation
- Active metabolites and parent compounds
- First-order vs nonlinear kinetics
- Detection windows vs half-life
- Reading labels and source quality
Read the medical disclaimer, methodology, and profile review log before using the model for comparison.