International Coffee Day: how much caffeine is too much for sleep

If you are awake at 2 a.m. on International Coffee Day, it may be worth thinking about what was in your cup yesterday afternoon. October 1 has been International Coffee Day since the International Coffee Organization launched it in 2015, and the UN General Assembly adopted the date in March 2026.

The FDA says most healthy adults can have up to 400 milligrams of caffeine a day without negative effects, which it describes as about two to three 12-ounce cups of coffee. The amount in a cup varies a lot. The FDA lists 113 to 247 milligrams for 12 ounces of brewed coffee, compared with about 71 for black tea and 37 for green tea. Energy drinks range widely, from 41 to 246.

Sensitivity also varies from person to person. According to the FDA, too much caffeine can bring on a fast heart rate, jitters, anxiety, headaches, an upset stomach, and insomnia or disrupted sleep. Caffeine can also hide in less obvious places such as energy bars, some pain relievers, chewing gum and ice cream. Pregnant people, children and anyone taking medications should ask a doctor or pharmacist about their own limits.

If you are a regular coffee drinker and want to cut back, the FDA suggests doing it gradually to avoid withdrawal headaches. Many people find it helps to set a personal cutoff time in the early afternoon and switch to decaf or herbal tea after that.

For tomorrow, try keeping a quick tally of every caffeinated drink and when you had it. One day of notes can show whether that afternoon cup is part of why you are up right now.