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

“The moment your adrenaline hits, it kind of stimulates the release of sugar stores from your liver, and then you get a crash,” says Akkerman. “And if you haven’t eaten anything, you can get hypoglycemia, which can make you really shakey on top of everything else.”

The solution, says Akkerman, is to have some complex carbohydrates and proteins. This can be anything from granola to peanut butter toast. The extra energy from food will keep your body from crashing 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 really 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 taller than others. But the general rule from the U.S. Food and Drug Administration is that 400 milligrams of caffeine per day is the highest dose that has been shown to be safe for most people.

That could be four 8-ounce cups of drip coffee or three double shots of espresso. If you are pregnant, the safe dose might be half this amount.

But people can also differ greatly in their ability to metabolize caffeine. “There’s actually a genetic test you can take — it’s the CYP1A2 gene — that can tell you whether you metabolize caffeine slowly or quickly,” says Zumpano. But for the most part, she says, the key lies in listening to your body. If you experience a racing heartbeat or palpitations, you’ve probably consumed too much caffeine.

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

“I’m a cardiac dietitian,” Zumpano says. “So I see a ton of people with arrhythmia, tachycardia, fibrosis A – all of those things are made much worse by caffeine. Caffeine is one of the first things I take people off of, and it really regulates their heart rate.”

Stop drinking coffee late in the afternoon

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

But Europeans also tend to have a different circadian rhythm than Americans, Zumpano notes, with downtime in the afternoon. They also don’t drink their coffee from a 10 ounce cup.

As a general rule, Akkerman and Zumpano say, most people should stop drinking coffee at 3 p.m., or even midday. This will depend on how much coffee you drink each day and how quickly your body metabolizes caffeine. Although many people can still sleep after consuming caffeine late in the day, Zumpano says, it often has subtle effects on the quality of your sleep. Cortisol only leaves your body slowly.

“I have patients who tell me, ‘I can have caffeine any time and it doesn’t affect my sleep,’ says Zumpano. “And I say, ‘Why don’t we just try to get rid of it?’ And they say, “My God, I sleep so much better.” I sleep all night. I didn’t know it was possible.’

Don’t switch to tea late in the day

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

Tea generally contains less caffeine than coffee. On average, a cup of tea contains half to three-quarters the amount of caffeine found in a cup of tea. But the reason it’s smoother isn’t due to the lack of caffeine. Instead, tea releases caffeine much more slowly. The phenols in tea slow down the rate at which your body processes caffeine, leading to a much more regal and civilized feeling.