Everybody handles caffeine differently, but there is a general consensus that drinking coffee and other stimulating beverages late at night can keep you up way past bedtime.

So, is there a cut off for the last cuppa joe or caffeinated tea? Experts say it’s at around nine hours before you intend to go to sleep.

That’s because it can double the amount of time you need to be able to fall asleep and get the 7-9 hours of shut-eye adults need for the best overall health, according to federal guidance.

“If you plan to go to bed at 9 p.m. If you are sensitive to caffeine, I would say to stop drinking it around noon,” Roberta Anding, registered dietitian and an assistant professor at the Baylor College of Medicine, said in a previous statement.

“Drinking caffeine before bed will impact your sleep. The average person takes about 10 to 20 minutes to fall asleep. If you have caffeine in your system or are sensitive to it, this amount of time can double,” she explained.

Caffeine impacts the body in several ways, allowing blood to flow more freely, preventing drowsiness and spiking adrenaline, according to Henry Ford Health.

Over time, it’s been believed that people who regularly ingest caffeine can build up a tolerance. Still, the data on the theory is “surprisingly scarce,” Dr. Trisha Pasricha, an assistant professor of medicine at Harvard Medical School, wrote in a piece in The Washington Post.

There is a variant of a gene known as CYP1A2 that helps the body better break down caffeine, according to the Cleveland Clinic. Only about half of people have it, past research shows.

For most people, the impact doesn’t end when the buzz fades, registered dietitian Jane Leverich told Good Houskeeping.

“Caffeine can still delay melatonin, disrupt your circadian rhythm and reduce sleep quality in ways your body notices long before your brain does,” she said.

Caffeine has a fairly long half-life of around 4.5 hours, too, Anding said. That refers to the time it takes for its effects to wane by half.

But the amount and type of caffeine you’re drinking matter just as much as when you drink it.

An eight-ounce cup of coffee has around 100 milligrams and up to 400 milligrams a day is considered safe for most adults, the Mayo Clinic notes.

However, different kinds of coffee may contain different levels of caffeine. Instant coffee has less caffeine than fresh-brewed coffee, for example. Some teas may have even more caffeine than coffee, including matcha and black tea.

Lower caffeine drinks are simply safer closer to bedtime, and decaf may impact your sleep less. Although, decaf still contains some caffeine.

That’s why sensitive people should forgo a cup altogether unless it’s mid-day.

“Someone who metabolizes caffeine slowly should probably avoid evening caffeine if they want a good night’s rest,” Cleveland Clinic registered dietitian Anthony DiMarino advised.