Articles
Coffee, caffeine, and sleep — practical, science-backed reads.
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Swiss Water vs. EA decaf: which process is best?
Swiss Water, sugarcane EA, CO₂ or methylene chloride? How the decaf methods compare on taste, chemistry and safety — and how to pick the best specialty decaf.
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What is half-caf? The specialty lover's evening 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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Does dark roast have more caffeine than light roast?
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 & other 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? What the evidence says
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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Why doesn't caffeine affect you?
Some people barely feel caffeine — usually tolerance, fast metabolism or their genes. But here's the catch: not feeling it doesn't mean your sleep is safe.
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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 night after coffee?
Fall asleep fine but wake at 3am? Caffeine's long tail lightens your sleep and makes you surface in the second half of the night. Why, and how to fix it.
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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. Plus the blood-test exception.
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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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Caffeine and menopause: what to know
Caffeine can make some menopause symptoms harder — hot flashes, sleep, anxiety — for some women. What the research suggests, and how to enjoy coffee anyway.
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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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Caffeine and jet lag: timing coffee when you travel
Caffeine can help beat jet lag — if you time it to the destination clock. Morning coffee keeps you alert; a late cup wrecks your reset. How to time it right.
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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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Caffeine on night shifts: timing your last coffee
Night-shift caffeine advice, rebased: the "stop by 2 p.m." rule doesn't fit when you sleep in the morning. How to time your last coffee to your schedule.
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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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Does caffeine affect deep sleep?
Falling asleep fine after a coffee doesn't mean you slept well. How caffeine trims deep sleep — and why your tracker sees what you can't feel.
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Does decaf have caffeine? What's really in your cup
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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Why can't you handle caffeine like you used to?
Coffee you slept through at 25 now keeps you up. It's mostly your sleep changing with age, not caffeine lingering longer — and here's how to adjust.
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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 does skipping coffee give you a headache?
Skip or delay your usual coffee and a headache creeps in. Why it happens, why it hits on weekends, how long it lasts, and how to avoid the dip.
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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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Why does coffee make you feel anxious?
Coffee can leave you jittery, tense, or on edge — caffeine's stimulant effect, not a flaw. Why it happens, and how to keep your coffee without the edge.
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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 vs slow caffeine metabolizers: the genetics (CYP1A2)
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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Caffeine calculator: when does caffeine leave your system?
How a caffeine calculator estimates what is left in your body over time, what it needs to be accurate, and how CaffIQ does it in real time.
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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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How much caffeine is in coffee, tea & energy drinks?
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.