If you’re like most adults, enjoying two cups of coffee or tea in the morning won’t have any impact on your bedtime. But there is a direct relationship between age and caffeine. So if you’re celebrating another milestone birthday or especially sensitive to caffeine, you might need to change up your A.M. ritual, and certainly avoid it later in the day.

Turns out young people are able to metabolize caffeine more quickly than older adults. One study that looked at the metabolic clearance of several substances, including caffeine, in a group of 65- to 70-year-olds found it takes seniors 33% longer to metabolize caffeine compared to younger adults.

For most people, 200 to 300 mg of caffeine consumed early in the day won’t have a negative impact on sleep. “The half life of caffeine is close to six hours,” says Michael T. Smith, PhD., a Fitbit sleep advisor and director of the Center for Behavior and Health at Johns Hopkins University School of Medicine. “So if you put 200 mg of caffeine in your system at 4pm, you will still be processing about 100 mg at 10pm.” As you age, your body needs even more time (33% more!) to fully process the stimulant. Which means the espresso you drank late-morning could very well still be keeping you up at night, he explains.

Coffee, tea, cola, energy drinks, chocolate, some over-the-counter medications—you should think twice before consuming any of these items, if you’re getting older or sensitive to caffeine. Here’s how they add up:

• One 6-ounce cup of coffee, about 100 mg of caffeine

• One 6-ounce cup of tea, about 70 mg of caffeine

• One 12-ounce serving of cola, about 50 mg of caffeine

• One ounce of chocolate, about 6 mg of caffeine

• One tablet of OTC, extra-strength headache reliever, about 65 mg of caffeine

If you’re having trouble falling asleep at night, consider cutting back or completely eliminating caffeine from your diet, and talk to your doctor about ways to help you get more rest.