The Best Time to Drink Coffee for Productivity (and When Not To)

“Right when your adrenaline hits, it kind of boosts the release of sugar stores from your liver, and then you get a crash,” Akkerman says. “And if you haven’t eaten anything, you can get hypoglycemic, which can make you really shaky on top of everything else.”

The solution, says Akkerman, is to have a little complex carbohydrates and proteins. This might be anything from granola to peanut butter toast. The extra energy from the food will stop your body from crashing out mid-morning.

This, I learned from Akkerman, is the root of my mid-morning shakes. It wasn’t the caffeine. It was adrenaline and hypoglycemia. I’m not much of a breakfast person, but on Akkerman’s advice, I now eat a handful of peanuts each morning before my morning brew, to avoid an unexpected sugar crash.

Moderate Your Caffeine Dose

Some people process caffeine quickly and well. Some people don’t. Some people are also bigger than others. But the general rule of thumb from the US Food and Drug Administration is that 400 milligrams of caffeine per day is the highest dose that’s been demonstrated to be safe for most people.

This might amount to four 8-ounce mugs of drip coffee or three double shots of espresso. If you’re pregnant, the safe dose might be half this amount.

But people can also differ wildly in their ability to metabolize caffeine. “There’s actually a genetic test you can take—it’s the CYP1A2 gene—that can tell you if you’re a slow or fast metabolizer of caffeine,” says Zumpano. But for the most part, she says, the key lies in listening to your body. If you’re experiencing racing heartbeats or palpitations, you probably have had too much caffeine.

The same is true, she says, if you feel a hollow, heady combination of “wired but also tired” in the afternoon—a common feeling that is often the result of high adrenaline or cortisol-fueled stress levels combined with a post-lunch sugar crash.

“I’m a cardiac dietitian,” Zumpano says. “So I see a ton of people with arrhythmia, tachycardia, A-fib—all of those things are way worsened by caffeine. Caffeine is one of the first thing I take people off of, and it really does regulate their heart rhythm.”

Stop Drinking Coffee by Late Afternoon

I know, I know. It’s civilized in France to take a little cup of coffee after dinner.

But Europeans also tend to be on a different circadian rhythm than Americans, Zumpano notes, with downtime in the afternoon. They’re also not drinking their coffee from a 10-ounce mug.

As a rule of thumb, say Akkerman and Zumpano, most people should stop drinking coffee by 3 pm, or maybe even at noon. This will depend on how much coffee you drink each day and how fast your body metabolizes caffeine. Even though many people can still sleep after consuming caffeine late in the day, Zumpano says, it often still quietly has effects on your sleep quality. Cortisol leaves your body only slowly.

“I have those patients who are like, ‘I can have caffeine anytime, and it doesn’t affect my sleep,’ Zumpano says. “And I say, ‘Why don’t we just try to get rid of it?’ And they’re like, ‘My gosh, I’m sleeping so much better. I sleep through the night. I didn’t know that was possible.’”

Don’t Switch to Tea Late in the Day

Akkerman, the neurologist, also cautions against switching to tea in the afternoon—a fairly common habit among those who don’t want dramatic caffeine spikes in the afternoon.

Tea generally has less caffeine than coffee. On average, a cup of tea has half to three-quarters the amount of caffeine in a mug of drip. But the reason it feels gentler is not for lack of caffeine. Rather, tea releases caffeine much more slowly. Phenols in the tea slow the rate at which your body processes caffeine, leading to a much more stately and civilized feeling.