Articles
Practical, sourced articles on coffee, caffeine and sleep: how long caffeine lasts, how much is in your drink, and when to have your last cup.
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How to choose a caffeine tracker app
Estimates, personalization, fast logging, privacy, pricing: what actually matters in a caffeine tracker app, and the red flags worth walking away from.
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Why is your sleep score so low?
Woke up feeling fine to a low sleep score? What your watch or ring really measures, the usual suspects, and the one almost nobody thinks to check.
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Why is your HRV low in the morning?
Woke up to a low HRV reading? What heart rate variability measures, why one low morning is normal, the usual causes, and the one nobody thinks to check.
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Can't get out of bed in the morning?
Your alarm goes off and your body just says no? Why mornings feel so hard, even after a decent night, the usual causes, and the one most people miss.
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Is your teen still up at 1 a.m.?
Your teen can't fall asleep at night, then can't get up for school? Why the teenage body clock runs late, what makes it worse, and how to help.
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Hitting a wall at 11 a.m.? The mid-morning slump
Already fading and it isn't even lunchtime? Why the mid-morning slump hits, what's usually behind it, and how to make it through the late morning.
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Can't sleep on Sunday nights?
Wide awake Sunday night and wrecked by Monday morning? Why Sunday is so often the worst night of the week, the usual causes, and the one nobody suspects.
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Can't turn your brain off at night?
Lights out, and your mind replays the day and starts on tomorrow's list? Why your brain revs up at bedtime, the usual causes, and the one nobody suspects.
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Tired all morning, wired at night?
Dead to the world until noon, wide awake at 11 p.m.? Where that late-night second wind comes from, why it feeds itself, and how to flip your days back.
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Can't sleep, but you don't drink coffee?
Restless nights even though you're careful about everything? The most common reasons sleep goes wrong, and the one hiding where nobody thinks to look.
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Bad sleep after a night out?
Home late, a little buzzed, and a short, choppy night? Why sleep goes sideways after a night out, the usual causes, and the one nobody counts.
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Can't nap, even when you're exhausted?
Wiped out after lunch, yet wide awake the second you lie down? Why naps won't come, the usual reasons, and the one almost nobody thinks of.
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New parent and running on empty?
Nights in pieces, days on autopilot? What makes the exhaustion of the first months with a baby heavier than it has to be, and what helps, guilt-free.
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Shaky hands in the afternoon?
A slight tremor when you hold your phone, that wired, jittery feeling mid-afternoon? The usual causes, the one people overlook, and when to see a doctor.
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Sleeping worse since starting the pill?
Your nights changed after you started or switched birth control pills? What's actually known about the link, the other likely causes, and a simple test.
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Can't sleep the night before a race?
Race, game or tournament tomorrow, and you're lying there wide awake? What one short night really costs, the usual causes, and the one nobody counts.
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Doze off on the couch, then wide awake in bed?
Out cold on the couch, then staring at the ceiling the minute you're in bed? Why sleep slips away on the way to the bedroom, and the cause nobody checks.
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The 3 p.m. slump: where it comes from
Heavy eyelids and a foggy brain around 3 p.m.? Where the afternoon slump comes from, what makes it worse, and how to get past it without losing sleep.
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Can't sleep after an evening workout?
Wiped out after the gym, then wide awake in bed? Why a late workout sometimes wrecks your night, and how to keep both your training and your recovery.
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How much caffeine is in a Nespresso capsule?
An Espresso capsule holds 55–65 mg of caffeine, a Lungo 77–89 mg, and a large Vertuo up to 200 mg. The real figures, range by range.
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Capsules, pods or ground: where is the caffeine?
France's ANSES measured 150 mg per 100 ml in a capsule against 50 mg in filter coffee. But in the cup the ranking flips — here is why, format by format.
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Does a lungo capsule have more caffeine?
A lungo capsule holds 77–89 mg against 55–65 mg for an espresso. But stretching an espresso capsule with the button adds almost nothing. Here is why.
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How much caffeine in a coffee shop espresso?
An espresso served across a counter runs 60 to 80 mg — usually the top of that range. What is really in the cup, and why two cafés never match.
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Does a ristretto have less caffeine?
Yes, slightly — and it is the opposite of what it tastes like. Between a ristretto and a long shot the real gap is about ten milligrams.
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Does chicory coffee have caffeine?
Chicory root itself has none at all. But most drinks sold as chicory are blends — and one popular one carries 64 mg a cup, as much as an espresso.
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ANSES on caffeine: what France's agency says
The French food-safety agency sets no maximum dose. It measures what people actually drink, and rules on two specific pairings. Here is the detail.
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Can you drink coffee before a blood test?
Labs define fasting as nothing but water — coffee is outside it, even black. What they ask for, and why the answer changes with the test.
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How much caffeine is in a Red Bull?
80 mg in the 250 ml can, 114 mg in 355 ml, 151 mg in 473 ml. The concentration never changes — the size decides, not the recipe.
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How much caffeine is in a Coca-Cola?
About 34 mg in a 355 ml can, roughly a third of a coffee. And Diet Coke holds more than the classic — 46 mg. The figures, variant by variant.
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How much caffeine from a bean-to-cup machine?
A bean-to-cup espresso holds 70–90 mg against 55–65 for a capsule. The gap is the dose of grounds — and that is the one you set yourself.
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Is a decaf capsule really caffeine-free?
Nearly, not quite: 3–6 mg in an Original capsule, up to 11 in a Vertuo. Ten to twenty times less than a regular capsule, without being zero.
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How much caffeine is in instant coffee?
About 30 mg per level teaspoon, so around 60 mg for a two-spoon cup. The real variable isn't the brand — it's your hand.
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Coffee with dessert: what it costs your night
An espresso served with chocolate petits fours is 70–100 mg, not 60–80. And it arrives at the most expensive hour of the day.
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Does milk change the caffeine in your coffee?
It holds none and removes none. A cappuccino and a macchiato weigh the same: 60 to 80 mg. Only the number of shots counts.
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What the "high caffeine content" label means
A mandatory statement above 150 mg per litre. But an espresso runs at 1,500 mg/L and carries nothing — because the rule sorts by category, not by dose.
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Trouble sleeping during Ramadan?
Short nights split in two, long days, and a tiredness that won't lift? Why sleep takes a hit during Ramadan, the usual causes, and what helps you recover.
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Coffee on long drives: what actually works
Caffeine masks fatigue, it doesn't remove it. Why a coffee taken too late arrives after the fact, and why the coffee nap is the one combination that works.
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How much caffeine is in a Monster?
160 mg in the 500 ml can. The same concentration as a Red Bull — 32 mg per 100 ml — so the can size is the entire difference.
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How much caffeine is in a Starbucks coffee?
From 75 mg for a latte to 410 mg for a venti brewed coffee. Black coffee climbs highest — and going up a size doesn't always add coffee.
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Is restaurant decaf really decaf?
Yes — 'decaffeinated' is a regulated category, not a marketing claim. Reckon on 5 to 15 mg in the cup against 60 to 80 for a regular coffee.
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Is caffeine a banned substance in sport?
No: WADA removed it from the Prohibited List on 1 January 2004. It stays on the Monitoring Program, which is not remotely the same thing.
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Energy drinks and minors: what French law says
Contrary to widespread belief, no French law bans selling them to minors. What does exist: a mandatory label and a ban inside schools.
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Why caffeine guidelines differ between countries
Everyone agrees on 400 mg a day. The divergences are elsewhere — and the trap is that a US 'cup' is 355 ml, not an espresso.
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Can't sleep before a big exam?
Wide awake the night before a test, flashcards still running through your head? Why sleep won't come, what helps, and the cause nobody suspects.
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Should you drink less coffee in hot weather?
Heat changes almost nothing about caffeine. What changes is the format: switching from espresso to iced coffee can triple the dose unnoticed.
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Split shifts: where to put your coffees
Two services, two peaks of alertness, and a 1 a.m. bedtime. 'Nothing after 2 p.m.' stops meaning anything — here's what to anchor the last coffee to.
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The mid-morning coffee: a good moment?
Yes, one of the best of the day. Not for cortisol reasons: because twelve hours remain before bed. The awkward moment is 4 p.m.
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Does bottled iced tea have caffeine?
Yes, but very little: about 4 mg per 100 ml, so roughly 14 mg a bottle. Four to five times less concentrated than brewed tea.
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Guarana sodas: is the caffeine hidden?
Not hidden, just differently named: guarana's caffeine isn't called caffeine on the label. In a soda it stays very low all the same — 10 to 15 mg.
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Swiss Water vs. EA decaf: which process is best?
Swiss Water, sugar cane EA, CO₂ or methylene chloride? How the decaf methods compare on taste, chemistry and safety — and how to pick the best decaf.
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What is half-caf? The evening coffee trick
Half-caf is part regular, part decaf — about 45–50 mg of caffeine a cup instead of 95. What it is, the caffeine math, how to make it, and when to reach for it.
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Dark or light roast: which has more caffeine?
No — roast level barely changes caffeine. Why 'strong' isn't 'caffeinated', the scoop-vs-weight twist behind the myth, and what really drives your dose.
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Robusta vs. arabica: which has more caffeine?
Robusta has about twice the caffeine of arabica — roughly 2.2–2.7% vs 1.2% by weight. Why, how they taste, where each shows up, and what it means for your cup.
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Does your brew method change the caffeine?
Yes, but mostly through dose and contact time, not magic. How grind, heat, steep and ratio shape your cup — and how the common brew methods compare.
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How much caffeine is in tea? Green, black & more
A cup of tea has ~20–70 mg of caffeine — less than coffee. The mg by type (black, green, white, oolong), what changes it, and the tea-vs-coffee myth.
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Yerba mate, guarana & natural caffeine sources
Caffeine is the same molecule whatever the plant. Yerba mate, guarana, cacao, kola & more — the mg, and why 'natural' doesn't mean gentle.
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Does coffee sober you up? The dangerous myth
No — coffee makes you feel alert but doesn't lower your blood alcohol. Why 'wide-awake drunk' is dangerous, and what actually sobers you up (only time).
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Does coffee stunt your growth? No — here's why
No — there's no good evidence coffee stunts growth. Where the myth came from, what really sets your height, and what actually matters for kids and caffeine.
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How to get rid of caffeine jitters fast
No instant antidote — only time — but you can take the edge off in minutes. Stop, hydrate, eat, walk, breathe: what works, and when to get help.
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Why does coffee make you poop?
For about a third of people, coffee triggers the urge — often within minutes. And it's mostly not the caffeine: decaf does it too. Here's the real reason.
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Coffee on an empty stomach: good or bad idea?
For most people it's fine — no, it won't ruin your stomach. But coffee raises acid, and without food some get reflux, nausea or stronger jitters. What to do.
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Can you be intolerant or allergic to caffeine?
A true caffeine allergy is real but rare. What most call 'intolerance' is high sensitivity — from your genes. How to tell them apart, and what to do.
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Does caffeine raise your blood pressure?
Yes — caffeine causes a small, temporary rise, usually a few to ~10 mmHg. Why it happens, whether it lasts, and who should be careful. Not medical advice.
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Does coffee cause acid reflux or heartburn?
For some people, yes — coffee can relax the valve above your stomach and raise acid. Why it happens, whether decaf helps, and how to drink with less heartburn.
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Still tired no matter how much coffee you drink?
You push through the day and still feel flat? Where that stubborn tiredness comes from, the cause almost everyone overlooks, and a simple one-week test.
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Do men and women process caffeine differently?
Yes — but it's hormones, not sex. The pill roughly doubles how long caffeine lasts and pregnancy slows it more. What changes, why, and what it means.
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How long to build (or lose) caffeine tolerance?
Caffeine tolerance builds within days and firms up over 1–2 weeks — and a 1–2 week break resets it. The timeline both ways, and how to keep caffeine working.
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Why do you wake up at 3 a.m.?
Wide awake at 3 a.m. again? Why it's so often that exact hour, the most common causes, the one people overlook, and how to figure out which one is yours.
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Does caffeine affect REM sleep?
Yes — caffeine can reduce and delay REM, the dreaming, memory stage. How it differs from its hit to deep sleep, and why evening coffee targets it.
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What is caffeine and how does it work?
Caffeine is a natural stimulant that blocks adenosine, the chemical that makes you sleepy — so it masks tiredness rather than adding energy. The full explainer.
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Does caffeine actually improve focus?
Yes — caffeine sharpens alertness, vigilance and reaction time, most when you're tired. But there's a sweet spot: too much wrecks focus. How to use it well.
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Caffeine and cortisol: does coffee spike stress?
Yes — caffeine can modestly raise cortisol, but the rise is small and regular drinkers build tolerance. The morning-timing myth, and whether it matters.
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Does caffeine boost metabolism or burn fat?
Yes — caffeine gives metabolism a small, temporary boost and nudges up fat burning. But it's modest, fades with tolerance, and isn't a weight-loss shortcut.
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Does coffee break a fast?
For most fasting goals, black coffee doesn't break a fast — it's near-zero calories. What does: milk, sugar, cream, syrups and butter.
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Coffee and migraines: help or trigger?
Caffeine can both help headaches (it's in many painkillers) and trigger migraines (too much, or missing your usual dose). Why moderation and consistency matter.
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Broken sleep in perimenopause?
You used to sleep straight through, and now your nights come in pieces? Why sleep changes in perimenopause, what's behind it, and what helps.
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Is coffee bad for your heart?
For most healthy people, moderate coffee isn't bad for the heart — studies don't link it to heart disease. The real effects, and who should be careful.
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Still jet-lagged days after your trip?
Up at 3 a.m. and fading by mid-afternoon, days after you got home? Why jet lag hangs on, what slows recovery, and how to get back on local time faster.
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How to cut back on caffeine without the headache
Cutting caffeine suddenly causes the headache — so taper gradually instead. Use half-caf and decaf to ease down, keep the coffee you love, and skip the pain.
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The pill and caffeine: why your coffee lasts longer
Estrogen in the combined pill slows caffeine's clearance, so its half-life roughly doubles — your coffee lingers longer and reaches into your night.
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Caffeine before a workout: how much and when?
Caffeine is a proven performance aid at ~3–6 mg/kg taken 45–60 min before. The catch: an evening pre-workout has a long tail that can cost your sleep.
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Caffeine and teens: what parents should know
No official safe caffeine level is set for teens. EFSA references ~3 mg/kg a day, energy drinks are the main concern, and teen sleep makes timing matter.
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Caffeine and breastfeeding: what the guidelines say
Only a small amount of caffeine passes into breast milk. Many authorities cite moderate intake as generally fine — with newborns the sensitive case.
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Caffeine and pregnancy: what the 200 mg limit means
Authorities commonly cite ~200 mg of caffeine a day in pregnancy. What the reference means, why clearance slows, and why your doctor guides your number.
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Should you wait 90 minutes for your first coffee?
Delaying your first coffee has a plausible cortisol-and-adenosine rationale but limited evidence. Worth a try — but the evening cutoff matters more.
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Can't sleep after a night shift?
Dead tired after your shift, yet wide awake again a few hours later? Why daytime sleep is so hard, the usual causes, and the one nobody mentions.
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Does coffee actually dehydrate you?
No — moderate coffee doesn't dehydrate you. The water in it outweighs caffeine's mild diuretic effect, so coffee counts toward your daily fluids.
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Do coffee naps actually work?
A coffee nap means drinking a coffee, then napping 20 minutes. Why the timing works, what the research shows, and the catch that can cost you your night.
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How long after coffee can you sleep?
You had a coffee too late — when can you actually sleep? Estimate when caffeine drops to a sleep-friendly level, with a worked mg-by-hour example.
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Coffee after dinner: pleasure or sleep thief?
An espresso after dinner is a lovely ritual — and a long caffeine tail. Whether it costs your sleep depends on you, the dose, and the clock.
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Tired after 8 hours of sleep?
Eight hours in bed and still groggy when you wake up? Why a full night might not feel restful, the usual causes, and the one almost nobody suspects.
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Does decaf have caffeine? Yes, a little
Decaf isn't caffeine-free — ~2–5 mg a cup versus ~95 mg for regular. What's really left, how it's removed, and why good decaf changes everything.
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Matcha vs coffee: why the energy feels different
Matcha usually has less caffeine than coffee, plus L-theanine — an amino acid that smooths the lift into calmer focus. Why the two feel different.
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Energy drinks vs coffee: what's really different?
Per serving, an energy drink and a coffee have similar caffeine. The real differences: the sugar, the hidden guarana caffeine, and how fast you drink it.
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Espresso vs filter coffee: which has more caffeine?
Espresso tastes stronger, but a single shot usually has less total caffeine than a mug of filter coffee. Why concentration isn't the same as dose.
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Does cold brew have more caffeine than hot coffee?
Cold brew often has more caffeine than hot coffee — ~150–240 mg a serving. Why the long steep wins, and how it differs from iced coffee.
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Quitting smoking makes your coffee twice as strong
Smoking speeds up caffeine metabolism, so quitting can roughly double the caffeine in your blood — and the jitters get blamed on nicotine.
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Can you drink coffee at night and still sleep?
Some sleep fine after an evening espresso — usually fast metabolizers or low responders. Why it happens, and the catch: sleeping isn't sleeping deeply.
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Sleeping worse since your 40s?
Same habits as at 25, yet your nights are lighter and choppier? What changes with age, the usual suspects, and the one almost everyone overlooks.
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Why doesn't coffee wake you up anymore?
If coffee barely registers, that's caffeine tolerance. Why it happens, why the sleep hit stays, and how to reset it without quitting.
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Why are you so sensitive to caffeine?
If half a cup leaves you wired, you may be caffeine-sensitive. The two kinds of sensitivity — clearance and response — and the ADORA2A gene behind it.
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Why do you get a headache every weekend?
Same headache every Saturday or Sunday? Why weekend headaches are so common, the usual culprits, and the one almost everyone overlooks.
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Coffee and heart palpitations: what to know
A fluttering or pounding heartbeat after coffee is common. Why caffeine can be the trigger, when to see a doctor, and how to track your intake.
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Too much caffeine: how to tell and what to do
Had too much caffeine today? You can't flush it out fast — but you can stop it getting worse, ride it out, and protect tonight. Plus when to seek help.
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On edge for no reason?
Short fuse, tight chest, everything grating on you, and no idea why? The most common reasons you feel on edge, and the one almost everyone overlooks.
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Why does coffee make you tired? The caffeine crash
The caffeine crash is the slump that hits after the lift. Why it happens — adenosine rebound, a sugar dip, hidden sleep debt — and how to avoid it.
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How much caffeine for your weight? The mg/kg rule
Caffeine works per kilogram of body weight, so 400 mg isn't universal. Here's how to work out your own reference — and why weight is only part of it.
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Does caffeine affect sleep? What the science says
How caffeine delays and lightens sleep, why timing matters more than total amount, and what you can do about it.
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How to find your personal caffeine limit
You can't look up your caffeine limit — you find it. A simple, no-DNA-test method to discover your own line in milligrams and by time of day.
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Fast or slow caffeine metabolism: the CYP1A2 gene
Why some people can drink espresso at night and others can't — the science of caffeine metabolism, the CYP1A2 gene, and what it means for you.
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How a caffeine calculator works
What a caffeine calculator actually computes, what it needs to be accurate, and where every one of them stops — including ours.
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How long does caffeine take to kick in?
Caffeine starts working in ~15–20 minutes and peaks around 30–60. Time your coffee ahead of when you need it — and what changes the speed.
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Caffeine in coffee, tea & energy drinks: the chart
A clear, sourced reference for caffeine content per drink — espresso, brewed coffee, tea, energy drinks, and soft drinks, in mg per serving.
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How much caffeine per day is safe?
General daily caffeine reference points, why your personal limit differs, and how to stay under it while still enjoying your coffee.
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How long does caffeine stay in your system?
Caffeine has a half-life of around five hours on average — but it ranges from two to ten. Here is what that means, and what makes your number different.
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When should you stop drinking coffee before bed?
There's no universal cutoff — it depends on your body. Here's what the science says about timing your last coffee, and how to find your own line.