how much caffeine is safe


HealthyWomen content is for informational purposes only. Please consult your healthcare provider for medical advice, diagnosis or treatment.


If you're like most adults, caffeine is part of your everyday routine. Millions of people consume this stimulant daily in forms like coffee or tea. They need it to wake them up and keep them alert and going.

Normally, it doesn't pose any health issues. But are you in a situation where you need to curb your habit?

Up to 400 milligrams (mg) of caffeine a day appears to be safe for most adults, according to the Mayo Clinic. How much is that? It's about the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks. (Note that the actual caffeine content in beverages varies widely.)

Think you may have a caffeine addiction? Here are some signs that you're consuming too much.

You're anxious.

Is your mind racing? Are you feeling stressed? Nervous? That may be due to excess caffeine consumption. It can increase existing anxiety—even cause anxiety in those who don't normally experience it. It acts a stimulant, triggering the adrenal gland to excrete more stress hormones like adrenaline. That increases your heart rate, making you feel more anxious.

You're running to the bathroom a lot.

You may be overdoing it if you constantly need to empty your bladder. Caffeine can act as a mild diuretic, stimulating frequent urination in some people. And if you're drinking caffeine and not getting enough water, you're not hydrating your system enough. (Urine that is dark yellow or orange is a sign of dehydration.) Try eating a healthy snack with your caffeine. Food will slow the fluid's movement through your digestive tract and stomach and eventually your bladder.

You're not getting enough sleep.

Trouble sleeping at night is a common and telltale sign that you're getting too much caffeine. Caffeine keeps you from falling asleep, shortening the length of time you get zzzs. So, while you may be drinking caffeine to help you on days when you didn't get enough shut-eye, you may just be creating a vicious cycle. And know that it takes about five or six hours for one half of the caffeine you consume to be eliminated and about a day for it to completely clear your system, says the National Sleep Foundation. Aim to drink your caffeine earlier in the day to promote a better night's slumber.

You're jittery.

Sure, coffee makes you more alert. But caffeine speeds your central nervous system, causing you to feel jumpy. So, you may have jitters, shakiness, tremors or restlessness. That's because caffeine may trigger certain hormones to be released like adrenaline. And that can create those jittery symptoms.

Your heart feels like it's racing.

If your heart feels like it's pounding or racing uncontrollably, you may be drinking too much caffeine. Caffeine is a stimulant that can increase your heart rate. If you drink too much caffeine, you may experience heart palpitations, where your heart feels like it's beating too fast or unnaturally. Your body reacts to caffeine by going into overdrive.

You have an upset stomach or diarrhea.

Caffeine may stimulate your gastrointestinal tract. That can lead to an upset stomach, nausea and diarrhea. Coffee, for example, is acidic, which can irritate your stomach lining and cause abdominal cramping. Its laxative properties (likely due to its acidity) can also give you diarrhea if you drink a few cups a day (even if you drink decaf). If you don't want to give up coffee, drink richer varieties like French roast or espresso, which are less acidic and contain less caffeine.

You have heartburn.

It's common to have heartburn when you consume caffeine because it's highly acidic. When you drink caffeine, the muscle at the end of the esophagus relaxes and allows food and stomach acid to come back up. That causes a burning feeling in your chest, known as heartburn. Even in normal doses, caffeine has been linked to an increased likelihood of heartburn.

You get headaches.

Some caffeine can help relieve a headache. In fact, caffeine is a common ingredient in many prescription and over-the-counter headache remedies, says the Cleveland Clinic. Through caffeine's effects on the central nervous system, it helps these drugs act more effectively. And it helps the body absorb headache medications quickly. But, if you drink too much coffee for a sustained amount of time, you can go through caffeine withdrawal about 12 to 24 hours after your last dose of caffeine, says the American Heart Association. And symptoms include headaches as well as anxiety, fatigue, drowsiness and depression.

Woman Talk
Everything you need to know about women’s health — in one place.