Your Body Almanac

High caffeine intake

Coffee, energy drinks or pre-workout, from first thing until late in the day.

For most healthy adults, up to about 400 mg of caffeine a day (about four 8-ounce cups of brewed coffee) is not linked to harm. Past that, or late in the day, caffeine shows up as poor sleep, jitters, a racing heart and an upset stomach. Sweetened coffee drinks and energy drinks add sugar on top.

01

Sleep that is shorter and lighter

Caffeine blocks a chemical that builds sleep pressure through the day, and it takes many hours to clear. Afternoon coffee can still be working at bedtime. Poor sleep then makes you reach for more caffeine the next morning, and the loop continues.

SourcesCaffeine: How much is too much? (Mayo Clinic)Spilling the Beans: How Much Caffeine Is Too Much? (FDA)
Set a caffeine cutoffDailyStop coffee, tea, soda and energy drinks by early afternoon, because caffeine's effects can last up to 8 hours. Keep a consistent sleep scheduleDailyGo to bed and get up at the same times every day, weekends included, and aim for at least 7 hours.
02

Jitters, anxiety and a fast heartbeat

Too much caffeine can cause shakiness, restlessness, anxiety, a pounding or fast heartbeat and headaches. Energy drinks and caffeine powders make it easy to take a large dose quickly. People differ a lot in how sensitive they are. Avoid pure or highly concentrated powdered caffeine. Less than half a teaspoon of pure caffeine can be a toxic dose.

SourcesCaffeine (MedlinePlus)Spilling the Beans: How Much Caffeine Is Too Much? (FDA)
Set a caffeine cutoffDailyStop coffee, tea, soda and energy drinks by early afternoon, because caffeine's effects can last up to 8 hours. Practice slow breathingDailyTake five minutes to breathe slowly and deeply, such as box breathing with a count of four for each step. Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty.
03

Heartburn and an upset stomach

Coffee can relax the valve at the top of your stomach and trigger heartburn in some people, especially on an empty stomach. Many people find coffee on an empty stomach also loosens their bowels.

SourcesEating, Diet, and Nutrition for GER and GERD (NIH NIDDK)Heartburn and acid reflux (NHS)
Include protein at each mealDailySpread your protein across breakfast, lunch and dinner instead of saving it all for one meal.
04

Sugar in the cup

Flavored lattes, sweetened cold brews and energy drinks can carry as much sugar as a dessert. A few a day adds up to a lot of added sugar.

SourcesCaffeine: How much is too much? (Mayo Clinic)
Limit sugary drinksDailySwap soda, sweet tea, energy drinks and juice drinks for water, sparkling water or unsweetened tea and coffee. Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty.

When to see a professional

Get medical help right away for chest pain, a very fast or irregular heartbeat, fainting or seizures after caffeine. Talk to a doctor about caffeine if you have heart rhythm problems, high blood pressure, anxiety, reflux, are pregnant or trying to become pregnant, or take medicines that interact with it.