# How long does caffeine last? Half-life, cut-off times and what slows it down

That afternoon coffee feels long gone by dinner, but a good share of it is still in your blood. Here’s how long caffeine really lasts, what changes it, how much is in your usual drinks and when to have your last cup.

Source: https://nourishandstrong.com/how-long-does-caffeine-last
Published: 2026-11-08
Updated: 2026-11-08
By: the Nourish & Strong team
General information, not medical advice.

**The short answer:** caffeine peaks in your blood within about an hour and you’ll feel it for 4 to 6 hours, MedlinePlus says. Its half-life in adults is about 3 to 7 hours, so half of it is still in your body that long after your last sip. Pregnancy, birth control pills and liver disease slow it down. Smoking speeds it up.

That’s why a 3 p.m. coffee can still matter at 11 p.m. Here’s what the half-life means in practice, and how to time your caffeine so it helps your day without costing your night.

## What is the half-life of caffeine?

The half-life of caffeine is about 3 to 7 hours in healthy adults, according to a 2017 review of caffeine safety. Half-life is the time your body takes to clear half of what you took in. After two half-lives, about a quarter is left. After three, about an eighth.

The range is wide because people break caffeine down at different speeds. Most of the work is done by enzymes in your liver, and their pace depends on your genes, your hormones and your liver health. The FDA notes there is wide variation in both how sensitive people are to caffeine and how fast they clear it.

## How long does caffeine stay in your system?

Caffeine stays in your system for many hours, long after the buzz fades. Here’s what happens to a 200 mg dose, about two 8-ounce cups of brewed coffee, taken at 2 p.m. if your half-life is 5 hours, the middle of the usual range:

| Time | Hours since | Caffeine left (approx.) |
| --- | --- | --- |
| 2 p.m. | 0 | 200 mg |
| 7 p.m. | 5 | 100 mg |
| Midnight | 10 | 50 mg |
| 5 a.m. | 15 | 25 mg |

This is simple math on an average, and your own numbers may differ. With a 7-hour half-life, you’d still have around 75 mg on board at midnight. In late pregnancy, it could be far more.

## What makes caffeine last longer?

Pregnancy, birth control pills, liver disease, heavy drinking and some medicines make caffeine last longer. Smoking does the opposite. These figures come from published research:

| Factor | Effect on caffeine | Source |
| --- | --- | --- |
| Pregnancy | Half-life rose from about 3 hours to 10.5 hours in the last 4 weeks of pregnancy in one study, and starts rising early on | Knutti, 1982 |
| Birth control pills | Tend to double the half-life | Temple review, 2017 |
| Liver disease | Half-life may be longer | Temple review, 2017 |
| Heavy alcohol use | Longer half-life, slower clearance | Temple review, 2017 |
| Some medicines | Certain antibiotics, asthma medicines and heart medicines can interact with caffeine | MedlinePlus |
| Smoking | Doubles the rate caffeine is cleared | Temple review, 2017 |

If you take a regular medicine, ask your pharmacist whether it affects caffeine. Keep taking it as prescribed while you ask.

## How much caffeine is in coffee, tea and soda?

An 8-ounce cup of brewed coffee has about 95 mg of caffeine, black tea about 47 mg and a 12-ounce cola about 33 mg, based on USDA FoodData Central values:

| Drink or food | Serving | Caffeine |
| --- | --- | --- |
| Brewed coffee | 8 fl oz | 95 mg |
| Espresso | 1 fl oz shot | 63 mg |
| Instant coffee, made with water | 8 fl oz | 62 mg |
| Decaf brewed coffee | 8 fl oz | 2 mg |
| Black tea, brewed | 8 fl oz | 47 mg |
| Green tea, brewed | 8 fl oz | 29 mg |
| Herbal tea | 8 fl oz | 0 mg |
| Cola, regular | 12 fl oz can | 33 mg |
| Diet cola | 12 fl oz can | 43 mg |
| Red Bull | 8.4 fl oz can | 75 mg |
| Monster | 16 fl oz can | 158 mg |
| Dark chocolate, 70 to 85% | 1 oz | 23 mg |

Real drinks vary a lot. The FDA puts a 12-ounce regular brewed coffee anywhere from 113 to 247 mg, and decaf at 2 to 15 mg per 8 ounces. Coffee-shop cups are often much bigger than 8 ounces, and some pain relievers and cold medicines contain added caffeine too. For energy drinks, our guide on [whether energy drinks are bad for your heart](https://nourishandstrong.com/are-energy-drinks-bad-for-your-heart) has the details.

## How much caffeine is too much?

For most healthy adults, the FDA cites 400 mg a day, about two to three 12-ounce cups of coffee, as an amount not generally linked with harmful effects. Treat it as a general figure. The FDA says weight, medicines, health conditions and personal sensitivity all change what counts as too much for you. Signs you’ve had too much include a racing heart, palpitations, jitters, anxiety, an upset stomach, headache and trouble sleeping.

Caffeine can also raise blood pressure, MedlinePlus notes. If yours runs high, our guide on [how to lower blood pressure](https://nourishandstrong.com/how-to-lower-blood-pressure) is worth a read.

## When should you stop drinking caffeine before bed?

Stop drinking caffeine at least 6 hours before bed, and earlier if you’re sensitive or your drinks are strong. In a 2013 study by Drake and colleagues at Henry Ford Hospital, healthy sleepers took 400 mg of caffeine at bedtime, 3 hours before or 6 hours before. Even at 6 hours, a sleep monitor showed they lost more than an hour of sleep. The authors suggested keeping substantial caffeine to before 5 p.m. for a typical bedtime.

Practical ways to make the cut-off stick:

- Count back from your bedtime. For an 11 p.m. bedtime, aim to finish by 5 p.m., or noon if you know caffeine hits you hard.
- Switch your afternoon cup to decaf or herbal tea so the habit stays and the caffeine goes.
- Watch for hidden sources after dinner, like cola, iced tea, dark chocolate and some pain relievers.
- If you’re lying awake, the NHS lists caffeine among the most common causes of insomnia.

How you lie matters too, and our guide to [the best sleeping position](https://nourishandstrong.com/best-sleeping-position) covers that half of a good night.

## How long does caffeine withdrawal last?

Caffeine withdrawal usually lasts 2 to 9 days. A major review of the research found symptoms typically start 12 to 24 hours after your last dose and peak at 20 to 51 hours. Headache showed up in about half of people in studies, along with tiredness, low mood, irritability, trouble concentrating and feeling foggy. Stopping even 100 mg a day can cause it.

The FDA says withdrawal isn’t considered dangerous but can be unpleasant, so cut back gradually. Swapping one cup a day for decaf or half-caf every few days is an easy way to do it.

## Who should be careful with caffeine?

MedlinePlus suggests checking with your provider about limiting caffeine if you:

- Are pregnant or breastfeeding. The NHS advises no more than 200 mg a day in pregnancy.
- Have insomnia or another sleep disorder
- Have migraines or frequent headaches, or anxiety
- Have acid reflux (GERD) or ulcers
- Have an irregular heartbeat or high blood pressure
- Take stimulants, certain antibiotics, asthma medicines or heart medicines

Children and teens should have less than adults. Get urgent help for chest pain, fainting, or a racing heart with shortness of breath. If you lean on caffeine just to get through the day, our guide on [why you might always be tired](https://nourishandstrong.com/why-am-i-always-tired) looks at the causes underneath. For the bigger health picture, read [is coffee good for you](https://nourishandstrong.com/is-coffee-good-for-you).

## Your next step

Write down tomorrow’s bedtime and count back at least 6 hours. That’s your last-cup time. If menopause is part of what’s keeping you up, our guide to [menopause and sleep](https://nourishandstrong.com/menopause-and-sleep) is a good next read.

## Quick questions

### How long does caffeine take to kick in?

Caffeine starts working fast. A 2017 safety review found it peaks in saliva about 45 minutes after you take it, and MedlinePlus says blood levels peak within an hour. You may keep feeling the effects for 4 to 6 hours, though the caffeine itself takes longer than that to clear from your body.

### How long does caffeine keep you awake?

Caffeine can keep you awake for 6 hours or more. In a 2013 study, 400 mg of caffeine taken 6 hours before bed still cut sleep by more than an hour on a sleep monitor. Because its half-life is about 3 to 7 hours, an afternoon coffee can still affect your sleep at night.

### How do you get caffeine out of your system?

Time is the only reliable way to get caffeine out of your system. Your liver clears about half of it every 3 to 7 hours, and none of our sources describe a proven way to speed that up. If you’ve had too much, stop taking more and get urgent help for chest pain or fainting.

### Is decaf coffee caffeine-free?

Decaf coffee isn’t completely caffeine-free. The FDA says an 8-ounce cup typically has 2 to 15 mg, compared with about 95 mg in regular brewed coffee, based on USDA values. That’s usually small enough for an evening cup, but if caffeine affects you strongly, the FDA suggests you may want to avoid decaf too.

### Can caffeine make you tired?

Caffeine can leave you more tired over time. Caffeine late in the day can cut into your sleep, so you wake up less rested and reach for more. Stopping suddenly also causes withdrawal tiredness and drowsiness for 2 to 9 days. A steady cut-off time at least 6 hours before bed can help break the cycle.

### Is 200 mg of caffeine a lot?

For most healthy adults, 200 mg of caffeine isn’t a lot. It’s half the 400 mg a day the FDA cites as not generally linked with harmful effects, and about two 8-ounce cups of brewed coffee. In pregnancy, though, the NHS advises 200 mg as the most you should have in a day.

This article is general information, not medical advice. If you’re pregnant, take regular medicines or have a heart condition, please ask your doctor or pharmacist how much caffeine is right for you.

## Sources

- [Temple JL et al. The safety of ingested caffeine: a comprehensive review. Front Psychiatry, 2017](https://pmc.ncbi.nlm.nih.gov/articles/PMC5445139/)
- [Knutti R et al. The effect of pregnancy on the pharmacokinetics of caffeine. Arch Toxicol Suppl, 1982](https://pubmed.ncbi.nlm.nih.gov/6954898/)
- [MedlinePlus. Caffeine](https://medlineplus.gov/caffeine.html)
- [FDA. Spilling the beans: how much caffeine is too much?](https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much)
- [USDA FoodData Central. SR Legacy food composition data](https://fdc.nal.usda.gov/)
- [Drake C et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med, 2013](https://pmc.ncbi.nlm.nih.gov/articles/PMC3805807/)
- [Juliano LM, Griffiths RR. A critical review of caffeine withdrawal. Psychopharmacology, 2004](https://pubmed.ncbi.nlm.nih.gov/15448977/)
- [NHS. Foods to avoid in pregnancy](https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/)
- [NHS. Insomnia](https://www.nhs.uk/conditions/insomnia/)