How much caffeine is safe per day?

The FDA recommends that healthy adults consume no more than 400 mg of caffeine per day — roughly 4 cups of brewed coffee. Pregnant or breastfeeding women should limit intake to 200 mg, and adolescents to 100 mg. Children under 12 should avoid caffeine entirely.

What is the half-life of caffeine?

Caffeine has an average half-life of about 5 hours in healthy adults, meaning half of the caffeine you consume is still in your body 5 hours later. Half-life varies from 3 to 7 hours based on genetics, pregnancy, smoking, and medications.

How long before bed should I stop drinking caffeine?

Because caffeine has a 5-hour half-life, you should stop consuming it at least 8 hours before bedtime. For most people, that means no coffee or energy drinks after 2 PM if you go to bed at 10 PM.

How much caffeine is in a cup of coffee?

An 8 oz cup of brewed coffee contains about 95 mg of caffeine. A single espresso shot has about 63 mg, and an instant coffee has about 62 mg. Decaf still contains about 2 mg per cup.

How much caffeine is in an energy drink?

An 8.4 oz Red Bull has about 80 mg of caffeine. A 16 oz Monster or Rockstar has about 160 mg. High-performance energy drinks like Bang can contain up to 300 mg per 16 oz can.

Can caffeine affect sleep?

Yes. Caffeine blocks adenosine receptors in the brain, which delays the onset of sleep and reduces deep sleep quality. To protect sleep, keep caffeine below 50 mg in the 8 hours before bedtime.

Caffeine Withdrawal Timeline

When you stop caffeine, withdrawal symptoms typically begin 12–24 hours after your last dose, peak at 20–48 hours, and resolve within 2–9 days. Enter your last dose time below to see where you are.

How long will withdrawal last?

When you stop caffeine, withdrawal symptoms typically begin 12–24 hours after your last dose, peak at 20–48 hours, and resolve within 2–9 days. See where you are in the process.

Last caffeine at

Now (current time)

Hours since last dose

9.8hrs

Current statusMild

0–12 hours

No symptoms yet. Caffeine is still active in your bloodstream (half-life ~5 hours).

Full withdrawal should resolve by 09:00 (day 10) — about 206 hours from now.

Full withdrawal timeline

00–12 hoursMild
No symptoms yet. Caffeine is still active in your bloodstream (half-life ~5 hours).
12–24 hoursModerate
First symptoms appear: mild headache, fatigue, irritability, and difficulty concentrating.
24–48 hoursPeak
Peak withdrawal. Headache becomes more severe, with low energy, low mood, brain fog, and muscle pain.
2–4 daysResolving
Symptoms start to ease. Headache intensity drops, energy slowly returns, mood stabilizes.
5–9 daysResolved
Most symptoms resolve. Sleep may still be adjusting. Cravings fade.

How to ease withdrawal

• Taper by 25% per week instead of quitting cold turkey
• Stay hydrated — water helps clear caffeine metabolites
• Take ibuprofen or acetaminophen for headache (avoid aspirin if sensitive)
• Get extra sleep; expect mild fatigue for 2–3 days
• Substitute with decaf or half-caff to preserve ritual

What caffeine withdrawal feels like

Caffeine works by blocking adenosine receptors in the brain. Adenosine is the molecule that builds up while you're awake and produces sleep pressure. When you drink caffeine daily, your brain grows more adenosine receptors to compensate. Stop suddenly and those extra receptors are suddenly wide open — flooded with adenosine, your body feels exhausted, headachy, and foggy.

The DSM-5 (the diagnostic manual used by psychiatrists) officially recognizes Caffeine Withdrawal as a psychiatric condition. Symptoms include:

Headache — the most common symptom, often diffuse and throbbing
Fatigue — pronounced sleepiness, yawning, low energy
Low mood / dysphoria — feeling flat, mildly depressed, or irritable
Difficulty concentrating — brain fog, slow thinking
Flu-like symptoms — muscle aches, heavy limbs, sometimes nausea
Constipation — caffeine stimulates bowel motility; without it, things slow down
Muscle stiffness — sometimes tremors or muscle pain

The timeline explained

0–12 hours: No symptoms yet

Caffeine has a 5-hour half-life. By hour 12, you're still carrying about 20% of your last dose. You feel fine.

12–24 hours: First symptoms

Caffeine drops below functional threshold. A mild headache begins at the back of the head. Energy starts to dip. Many people don't connect these symptoms to caffeine yet.

24–48 hours: Peak withdrawal

This is the worst part. Headache intensifies (often throbbing), fatigue becomes overwhelming, mood drops, and muscle aches appear. Brain fog is at its worst. Most people who fail at quitting caffeine do so in this window.

2–4 days: Symptoms ease

Headaches fade to a dull background. Energy slowly returns. Mood stabilizes. Sleep is still adjusting — you may sleep longer than usual but wake up groggy.

5–9 days: Resolution

Most symptoms resolve. Cravings diminish. Sleep normalizes. Some ex-drinkers report a sustained low-grade flatness for another 1–2 weeks before feeling "normal" without caffeine.

How to ease withdrawal

The single most effective strategy is tapering rather than quitting cold turkey. Reduce intake by 25% per week — for example, if you drink 4 cups of coffee a day, drink 3 for a week, then 2, then 1, then half-caf, then none. This stretches withdrawal across several weeks but each step is barely noticeable.

Hydrate aggressively — water helps flush caffeine metabolites and reduces headache intensity
Take ibuprofen or acetaminophen for headache (avoid aspirin if you have stomach sensitivity)
Sleep more — your body needs extra rest during withdrawal; expect 8–9 hours
Substitute with decaf or half-caf to preserve the ritual while reducing caffeine
Exercise — even light walking boosts natural endorphins that counter the low mood
Avoid pain relievers with caffeine — Excedrin contains 65 mg per caplet, which would reset your withdrawal

When to see a doctor

Caffeine withdrawal is unpleasant but not dangerous for most people. However, seek medical attention if you experience:

Severe, unrelenting headache that doesn't respond to OTC pain relievers
Vomiting that prevents keeping fluids down
Symptoms lasting more than 2 weeks
Severe depression or suicidal thoughts
Seizures (rare, but possible in extreme cases)

If you have an underlying anxiety or mood disorder, quitting caffeine can temporarily worsen symptoms. Talk to your doctor before quitting if this applies to you.