Caffeine: How Much Is Too Much?
Coffee, tea, soda, and energy drinks all contain caffeine, and many people drink it without thinking about how much. For most healthy adults, a moderate amount is fine. Problems start when the amount is high, or when caffeine comes too late in the day.
This guide covers the daily limit, how much caffeine is in common drinks, how to tell if you have had too much, and when to stop for better sleep. I also share a few simple swaps I would choose.
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Key Takeaways
- For most healthy adults, up to 400 mg of caffeine a day is not generally linked to negative effects.
- The amount in a cup varies a lot, especially for coffee and energy drinks.
- Tolerance differs from person to person, so your own limit may be lower.
- Limit caffeine in the 6 hours before bed, or the 8 hours before bed if you are sensitive.
- If you are pregnant or breastfeeding, ask your provider how much is right for you.
What Is the Daily Limit?
The FDA cites 400 milligrams a day for most healthy adults as an amount that is not generally linked to negative effects (1). That is about 2 to 3 large cups of coffee, 12 ounces each (1). This is a general guide and not a target. Many people feel fine with less.
How Much Is in Your Drink?
The amount changes a lot between drinks and brands. The FDA gives these typical amounts for a 12-ounce serving (1):
- Brewed coffee: 113 to 247 mg
- Black tea: 71 mg
- Green tea: 37 mg
- Caffeinated soft drinks: 23 to 83 mg
- Energy drinks: 41 to 246 mg
Decaf is not caffeine-free. It still has about 2 to 15 mg in an 8-ounce cup (1). This is small, but it can add up if you drink several cups, or if you are very sensitive.
Signs You Have Had Too Much
The FDA lists these effects of too much caffeine: a faster heart rate, heart palpitations, higher blood pressure, trouble sleeping, anxiety, jitters, an upset stomach, nausea, and headache (1). If you often feel this way, track what you drink for a week and see if it matches.
Many of these signs can have other causes. If your heart races, see Why Does My Heart Race for No Reason?. If you feel shaky, see Why Do I Feel Shaky?.
Why Your Limit May Be Lower
The FDA says tolerance varies widely, depending on body weight, medicines, medical conditions, and how fast your body clears caffeine (1). The Sleep Foundation reports that caffeine’s half-life ranges from about 2 to 12 hours between people (3). Nicotine use can shorten it by up to 50%, and in pregnancy it is twice as long (3).
The FDA advises people who are pregnant, trying to become pregnant, or breastfeeding to ask their health care provider whether they need to limit caffeine (1). Teens should avoid energy drinks, and the Dietary Guidelines say to avoid caffeinated drinks for children under age 2 (1).
Caffeine and Sleep
The Sleep Foundation puts the average half-life of caffeine at about 5 hours (2). It recommends limiting caffeinated food and drinks for at least 6 hours before bed, or 8 hours if you are sensitive to caffeine (2). So for an 11 p.m. bedtime, an afternoon cutoff of 3 p.m. or earlier is a reasonable place to begin.
I recommend choosing a clear cutoff time and keeping it every day. If you also wake up often at night, read Why Do I Wake Up Every Night?.
How to Cut Back Without a Headache
Many people get a headache or feel tired if they stop all at once. I recommend cutting back slowly over a couple of weeks. For example, replace one cup a day with a half-and-half mix of regular and decaf, then move to decaf or tea. Drink water as well. If you feel tired all the time, caffeine may be hiding a different problem, and Why Am I Always Tired? explains some common causes.
Products That Can Help
These items make it easier to enjoy a warm drink without too much caffeine.
Good Decaf Coffee
I pick decaf that says it was decaffeinated by a water process or similar gentle method, from a roaster that tells you the roast date. Fresh decaf tastes much better than old decaf. Remember that decaf still has a little caffeine (1).
Herbal Tea
Peppermint, ginger, and rooibos teas are good choices for the afternoon, because they do not contain caffeine. If you are pregnant or take medicine, check the ingredients with your provider first.
A Measuring Scoop or Kitchen Scale
A simple scale is enough. Coffee strength changes with how much you use, so measuring gives you a steady amount each day.
A Smaller Mug
Choose a mug of about 8 ounces. Large mugs can hold 16 ounces or more, which doubles the caffeine without you noticing.
An Insulated Water Bottle
Pick a bottle that keeps water cold and that you enjoy carrying. For ideas, see The Best Everyday Products That Help You Drink More Water.
Common Mistakes to Avoid
Counting Only Coffee
Tea, soda, energy drinks, and even decaf all add caffeine (1). Add up everything you drink in a day.
Drinking Caffeine Too Late
Caffeine stays in your body for hours (2). A late afternoon coffee can affect your sleep that night.
Relying on Energy Drinks
The amount in energy drinks varies widely (1). Check the label, and remember that a large can can contain two servings.
Using Caffeine to Cover Constant Tiredness
If you need more and more caffeine to get through the day, talk to your doctor about your sleep and energy.
Try This Week
Find out where you are with a simple check:
- Write down every caffeinated drink you have for three days.
- Add up the total, using the amounts in this guide.
- Choose a cutoff time at least 6 hours before bed, or 8 hours if you are sensitive.
- Replace your last caffeinated drink of the day with water or herbal tea.
Final Thoughts
Caffeine is fine for most adults in moderate amounts. The best limit is the one that lets you feel calm during the day and sleep well at night. Know what is in your cup, set a cutoff time, and adjust if you notice jitters or poor sleep. If you are pregnant, breastfeeding, or have a heart condition, ask your doctor what is right for you.
