How much caffeine is too much?

The fight has been raging for years: Is caffeine good for health, or is it just another ingredient in our favorite foods and drinks that leads to a life less well-lived? That all depends on how you consume it—and how much of it you consume.

Too much sugar and creamer turn even small amounts of coffee into a dessert that, if consumed regularly, may leave you with a long list of ailments. On the other hand, coffee sans-sweeteners falls into that prized category of foods that not only taste good, but are good for you in moderation, according to mounting evidence.

The same goes for tea. On its own, tea is a powerhouse of nutrition whose list of benefits is still growing after thousands of years. Adding in sugar is a quick way to turn those benefits into ancient history.

Other sources of caffeine boast the same stimulating effects, but few or none of the health benefits. Soft drinks, energy drinks, and chocolate aren’t most people’s idea of health foods (although dark chocolate has plenty of surprising benefits). So, for this article, we’ll stick to coffee and tea, where the best benefits can be found. But before you go chugging 20 cups a day to maximize those benefits, it’s important to remember that all foods—the healthy and not-so-healthy alike—bring the best benefits when consumed in moderation. Coffee and tea are no exceptions to the rule.

So how much caffeine should you be drinking? And where can we draw the line between enough caffeine and way too much?

Caffeine by the numbers

According to the Mayo Clinic, up to 400 mg of caffeine per day is safe for most adults—that’s roughly the amount you’d find in four 8 oz cups of brewed coffee or about 8 cups of black tea. It’s also roughly the amount you’d find in 10 cans of soda (please don’t drink that much) or two energy shot drinks (or that much either).

Experts say you can expect about 100 mg of caffeine per cup of coffee and 50 mg per cup of black tea, but that’s a rough estimate. The amount of caffeine in a brewed cup can vary widely—in coffee, it depends on the type of beans you use to brew a cup, the way they’re roasted (lighter roasts have more caffeine than darker roasts), the drinks they become (eg, an Americano vs an espresso), and the serving size. In tea, similar variables are at play, like the type of leaf—green tea typically has about 28 mg of caffeine per cup, while black tea has almost twice that amount.

The wide range of caffeine per cup of coffee was illustrated in a JAMA Internal Medicine study that involved more than half a million people. Researchers found that coffee drinking was associated with lower all-cause mortality, even among people who drank 8 or more cups per day. But were those people consuming 800 mg of caffeine? That’s anyone’s guess, because the study didn’t account for the quantity of caffeine being consumed. Participants saw the same mortality-delaying benefits whether the coffee was ground, instant, or decaffeinated—meaning their brewed cups could have ranged from 0 mg to 500 mg or more each, making it difficult to pinpoint participants’ total caffeine intake per day.

Experts at the Mayo Clinic acknowledge that while 400 mg of caffeine per day is a solid blanket recommendation, limits will differ from person to person and are dependent upon their preferred choice of caffeine, overall tolerance, and weight. If you’re looking for a personalized limit, try this handy calculator, which accounts for your weight and favorite type of coffee.

Qualifying your intake

Because of the variability of caffeine content in a cup of coffee or tea, the 400 mg benchmark isn’t always useful. For some people, it may be more advantageous to qualify, rather than quantify, their caffeine intake and adjust their habits accordingly.

The answers to the questions below can help you find the threshold between too much and just enough caffeine.

Is your caffeine intake causing side effects? If you’re drinking four or more cups of coffee or black tea per day and are experiencing headaches, nervousness, irritability, urination problems, fast heartbeat, or muscle tremors, try cutting back bit by bit. When side effects subside, you can stick to the current intake.

Are you feeling jittery (even a little)? Caffeine affects people differently. If you’re jittery after drinking coffee or tea, that means you could be more susceptible to caffeine’s other negative side effects. Tread lightly.

How well are you sleeping? Caffeine can quickly turn a healthy sleep schedule into a never-ending cycle of sleeplessness—and a quest for more caffeine to offset the ensuing fatigue.

Are you taking any medications or supplements that contraindicate caffeine consumption? Mixing caffeine with ephedrine, which is used in decongestants, can increase your risk of hypertension, myocardial infarction, or seizure. Theophylline, when mixed with caffeine, can increase the negative side effects of caffeine like nausea and heart palpitations. The herbal supplement echinacea can increase the concentration of caffeine in your blood, boosting its unpleasant effects.

The takeaway

If your biggest concern about caffeine is its health consequences, start with the source. Where are you getting it? Evidence suggests coffee and tea (without sugar) can bring amazing health benefits, while energy drinks and soda do the opposite. As for how much caffeine to consume, keep in mind the 400 mg per day limit set by reputable institutions like the Mayo Clinic. 

If you’re finding it hard to quantify your intake, measure your consumption against the way caffeine makes you feel. As long as caffeine isn’t giving you the shakes or causing you to lose sleep and you’re staying within the four cup per day limit, you’re probably making the most of caffeine’s notable health benefits.