Caffeine · Evidence identifiers checked 2026-10-11 · Version 0.1.0 · Not yet reviewed by a clinician
How Much Caffeine Is Actually in Your Drink
Why decaf is not caffeine-free, why pod coffee varies several-fold, and how to set a personal ceiling you can check against.
People manage caffeine by counting cups, but a cup is not a unit. Decaffeinated coffee measured in one study contained 0 to 13.9 mg of caffeine per 16-ounce serving, and decaf espresso from one outlet contained 3.0 to 15.8 mg per shot. Pod coffee ranged from 19 to 147 mg per serving across products, and that was 51% to 162% of what manufacturers stated, with larger servings delivering more. Against that spread, the useful reference point is the systematic review finding that up to 400 mg a day in healthy adults is not associated with overt adverse effects, and the controlled finding that 400 mg taken even six hours before bed reduced objective sleep time. Counting milligrams, not cups, is what makes those two facts usable.
Not medical advice. This is a plain-language summary of published research for generally healthy adults. It is AI-drafted, has not been reviewed by a clinician, and nothing here diagnoses or treats anything.
What the evidence supports
Decaffeinated coffee is not caffeine-free: measured content was 0 to 13.9 mg per 16-ounce serving across outlets, and decaf espresso from one outlet held 3.0 to 15.8 mg per shot. c-01
Pod coffee ranged from 19 to 147 mg per serving, which was 51% to 162% of manufacturers' stated values; larger servings delivered more caffeine. c-02
Up to 400 mg a day in healthy adults is not associated with overt adverse cardiovascular, behavioural, reproductive, acute or bone effects. c-03
400 mg taken even six hours before bedtime measurably reduced objective sleep time, and caffeine before sleep lengthens sleep onset and reduces total sleep time in a dose- and timing-dependent way. c-04c-05
One next step: Write down what you actually drank yesterday in milligrams, using the panel or the outlet's own figures, and total it.
The short version
A cup is not a unit
The assumption behind 'I only have two cups' is that cups are equal. Product testing says otherwise. Pod coffee ranged from 19 to 147 mg per serving across the products tested, which was 51% to 162% of what manufacturers stated. Two people drinking 'one pod each' can differ by more than a hundred milligrams, and neither of them knows it from the label alone.
Decaffeinated coffee measured 0 to 13.9 mg of caffeine per 16-ounce serving across outlets, and decaf espresso from one outlet held 3.0 to 15.8 mg per shot. On its own that is small. It matters in two situations: people who switch to decaf in the afternoon and have three or four of them, and people who are unusually sensitive to caffeine. For most people, decaf in the evening is still the better choice; it is simply not zero.
A systematic review found no overt adverse cardiovascular, behavioural, reproductive, acute or bone effects at up to 400 mg a day in healthy adults. Separately, a controlled trial found 400 mg taken even six hours before bedtime measurably reduced objective sleep time, and a meta-analysis found caffeine before sleep lengthens sleep onset and reduces total sleep time in a dose- and timing-dependent way.
Those two facts together explain why daily totals and timing are separate questions. You can be under 400 mg and still sleep badly, and you can sleep fine on more.
Counting milligrams sounds fussy, but it takes one pass: read the panel or the outlet's own figures for the drinks you actually have, write the numbers down once, and reuse them. After that, a daily total is arithmetic. What you should not do is treat a milligram count as a health score. It is a way of knowing what you consumed so that the two reference points above mean something for you.
Three common beliefs, checked against the product studies and reviews behind this page.
Pick what you believe first; the evidence answer is revealed after, so you can see where your assumption and the studies part company. Nothing is scored against you.
Decaf has no caffeine in it.
Measured decaffeinated coffee held 0 to 13.9 mg per 16-ounce serving across outlets, and decaf espresso from one outlet held 3.0 to 15.8 mg per shot. Small, but not zero.
As long as you stay under 400 mg, caffeine will not affect your sleep.
400 mg taken even six hours before bed reduced objective sleep time in a controlled trial, and a meta-analysis found dose- and timing-dependent effects on sleep onset and total sleep time. The 400 mg figure is about adverse effects in healthy adults, not about sleep.
Pod coffee ranged 19-147 mg per serving, so a one-off look-up removes most of the guesswork. Certainty: low. c-02c-01
Set a ceiling below 400 mg(2 min; $0)
Low
No overt adverse effects were found at up to 400 mg a day in healthy adults. Certainty: moderate. c-03
Set a timing cut-off too(1 min; $0)
Low
400 mg six hours before bed still reduced objective sleep time in a controlled trial. Certainty: moderate. c-04c-05
Keep drinking, stop counting(0 min; $0)
Low
If your sleep and your days are fine, the evidence does not demand a change. Certainty: moderate. c-03
Measure your drinks once
Find the caffeine content for the three or four drinks you actually have, write the numbers on a card, and reuse them. This is the option every other choice depends on, and it costs one evening.
Contents vary by batch and outlet, so the numbers are good estimates, not exact.
Pick a daily ceiling, ideally below 400 mg to leave room for the drinks you did not plan for, and total against it. If you are sensitive to caffeine, start lower and adjust by how you feel.
Requires honesty about the second and third drinks.
Choose a cut-off a fixed number of hours before your own bedtime and keep it for two weeks before judging. The trial used six hours; individual clearance varies, so treat six as a starting point rather than a rule.
Cuts out late coffee, which is exactly the cup some people want.
Nothing here says a healthy adult must track caffeine. If you sleep well, feel fine, and are not in a sensitive group, leaving it alone is a legitimate choice.
You will not notice a slow creep upward in total intake.
Build a personal drink list with milligram values and total a day against your own ceiling.
Free: personal drink list with your own mg values; daily total and headroom; text export and print; all citations and cautions Plus (optional, $5 one-time, price being tested): calendar (.ics) cut-off reminders; unlimited share images; share card without the 'Made with CortexLit' footer Works offline. No account. Every source and caution stays free.
Turn your bedtime and a buffer into a clock time, and show what a late drink costs you against the trial's six-hour test.
Free: cut-off time from your bedtime; comparison with today's last drink; text export and print; all citations and cautions Plus (optional, $5 one-time, price being tested): calendar (.ics) daily cut-off reminders; unlimited share images; share card without the 'Made with CortexLit' footer Works offline. No account. Every source and caution stays free.
Commercial disclosure: The companion apps have an optional paid Plus tier. All evidence, cautions, and the main takeaway are free. No affiliate links, no sponsors. Plus checkout isn't live yet.
Evidence cards
Each card links a claim from this page to its sources. "Certainty" is our informal editorial judgement of how sure we can be, based on study design, size, consistency, and how closely it fits everyday life. Sources were weighted by type: Cochrane and systematic reviews 1.0, guidelines 0.9, randomized trials 0.8, observational studies 0.5, lab, mechanism or animal work 0.2. That ranking isn't the same thing as certainty.
c-01 Decaffeinated coffee contained 0 to 13.9 mg of caffeine per 16-ounce serving across outlets sampled, and decaffeinated espresso from one outlet contained 3.0 to 15.8 mg per shot.
Certainty: lowObservational (association only)
Who was studied, what was found, and the limits
Who: Decaffeinated coffee and espresso products sampled from outlets Measured: Caffeine content per serving Finding: 0 to 13.9 mg per 16 oz; 3.0 to 15.8 mg per decaf espresso shot
Why this certainty: Direct product measurement, but a sample of outlets rather than a market-wide figure. (Informal editorial assessment, not a formal GRADE rating.)
Limits: One sampling exercise; contents vary by outlet, brand and batch. Applies to: Why 'decaf' still contributes to a daily total.
Identifier carried over from the 2026-10-11 abstract-level verification batch; not re-queried in this run. Source record
c-02 Caffeine in pod coffee ranged from 19 to 147 mg per serving across the pods tested, which was 51% to 162% of the manufacturer's stated values; larger serving sizes delivered more caffeine.
Certainty: lowObservational (association only)
Who was studied, what was found, and the limits
Who: Pod coffee products tested against stated values Measured: Caffeine per serving versus label Finding: 19 to 147 mg per serving; 51% to 162% of stated values
Why this certainty: Direct measurement, but one product family, and label accuracy is not a health outcome. (Informal editorial assessment, not a formal GRADE rating.)
Limits: One pod system; results may not generalise to all pods or brew methods. Applies to: Why pod users should read actual content rather than trust a stated number.
Identifier carried over from the 2026-10-11 abstract-level verification batch; not re-queried in this run. Source record
c-03 A systematic review found the evidence generally supports that up to 400 mg of caffeine a day in healthy adults is not associated with overt adverse cardiovascular, behavioural, reproductive, acute or bone effects; data are limited for children and teens and more research is needed in sensitive groups.
Who: Healthy adults across the evidence pooled in a systematic review Measured: Cardiovascular, behavioural, reproductive, acute and bone effects Finding: No overt adverse effects at up to 400 mg a day
Why this certainty: A systematic review across many outcomes, the strongest source type in this batch. (Informal editorial assessment, not a formal GRADE rating.)
Limits: Healthy adults; limited data for young people, pregnancy and sensitive groups. Applies to: The ceiling to total your intake against.
Identifier carried over from the 2026-10-11 abstract-level verification batch; not re-queried in this run. Source record
c-04 In a controlled trial, 400 mg of caffeine taken even six hours before bedtime measurably reduced objective sleep time compared with placebo.
Certainty: moderateHuman trials (cause and effect)
Who was studied, what was found, and the limits
Who: Healthy adults in a randomised crossover trial Measured: Objective sleep time after caffeine at 0, 3 and 6 hours before bed Finding: Reduced objective sleep time even at 6 hours before bed
Why this certainty: A controlled trial with objective sleep measurement at a defined dose. (Informal editorial assessment, not a formal GRADE rating.)
Limits: One dose (400 mg) in healthy adults; individual clearance varies. Applies to: Why timing needs a ceiling in milligrams, not a cup count.
Identifier carried over from the 2026-10-11 abstract-level verification batch; not re-queried in this run. Source record
c-05 A systematic review and meta-analysis found caffeine taken before sleep lengthens sleep onset latency and reduces total sleep time, with effects that depend on dose and timing.
Certainty: moderateHuman trials (cause and effect)
Who was studied, what was found, and the limits
Who: Studies pooled in a systematic review and meta-analysis Measured: Sleep onset latency and total sleep time Finding: Longer sleep onset and less total sleep; dose- and timing-dependent
Why this certainty: A meta-analysis pooling many studies with a consistent direction. (Informal editorial assessment, not a formal GRADE rating.)
Limits: Pooled doses and timings vary; individual sensitivity differs. Applies to: Setting a personal cut-off as well as a daily ceiling.
Identifier carried over from the 2026-10-11 abstract-level verification batch; not re-queried in this run. Source record
Where studies disagree
How precise is a labelled caffeine figure: One product study found pod coffee at 51% to 162% of stated values, while another found 84% of energy drinks matched their labels. Label accuracy differs by product category and market, so neither figure applies to all drinks. (src-02)
Sources for this entry
Every identifier below was verified against PubMed on 2026-10-11 in an earlier batch. This run carried the identifiers over rather than re-querying them, and no retraction database was checked. Verification was at abstract level; full text was not read.
Decaffeinated coffee contained 0 to 13.9 mg of caffeine per 16-oz serving across outlets; decaf espresso from one outlet contained 3.0 to 15.8 mg per shot.
Desbrow 2019 Desbrow B, Hall S, Irwin C. Caffeine content of Nespresso® pod coffee. Nutr Health. 2019;25(1):3-7. doi:10.1177/0260106018810941. PMID: 30392444. PMID 30392444 · observational study · confidence weight 0.5 · abstract level
Caffeine ranged from 19 to 147 mg per serving across pods and was 51% to 162% of the manufacturer's stated values. Larger serving sizes delivered more caffeine.
Wikoff 2017 Wikoff D, Welsh BT, Henderson R, et al. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol. 2017;109(Pt 1):585-648. doi:10.1016/j.fct.2017.04.002. PMID: 28438661. PMID 28438661 · systematic review · confidence weight 1.0 · abstract level
The evidence generally supports that up to 400 mg of caffeine a day in healthy adults isn't associated with overt adverse cardiovascular, behavioral, reproductive, acute or bone effects. Limited data exist for children and teens, and more research is needed on sensitive groups.
Drake 2013 Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-1200. PMID 24235903 · randomized controlled trial · confidence weight 0.8 · abstract level
400 mg caffeine taken even 6 hours before bedtime measurably reduced objective sleep time compared with placebo.
Gardiner 2023 Gardiner C, Weakley J, Burke LM, et al. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev. 2023;69:101764. PMID 36870101 · systematic review meta analysis · confidence weight 1.0 · abstract level
Caffeine taken before sleep lengthens sleep onset latency and reduces total sleep time; effects are dose- and timing-dependent.