When it comes to coffee, there tends to be two types of drinkers. There are those who get jittery after drinking half a cup and those who can drink an entire pot and still fall asleep at night.
Chances are if you identify with the latter, you’ve probably thought about whether this is a healthy habit. It’s easier to gauge if you’re having one too many cups if you feel its adverse effects. But what if you don’t? How can you tell if you’re drinking too much coffee?
According to the U.S. Department of Agriculture’s (USDA) Dietary Guidelines, most people probably shouldn’t drink an entire pot of coffee a day. “For the majority of healthy adults, consumption of up to 400 milligrams (mg) of caffeine a day appears to be safe,” says Lana Nasrallah, MPH, RD, LDN, clinical dietitian at UNC Health in Chapel Hill, North Carolina. “To put that in perspective, 4 to 5 cups of brewed coffee has just about 400 mg of caffeine.” FYI, that’s 8-ounce servings, and chances are you’re drinking 12 or 16 ounces at a time if you’re buying from your local coffee shop. Therefore, you would reach that limit much quicker.
As it turns out, though, exactly how many cups of coffee you can safely drink depends on a few things. This includes how sensitive you are to caffeine, whether or not you have any health conditions that don’t mix well with the stimulant, and how your coffee is brewed.
Caffeine content in coffee
“It’s important to note that the amount of caffeine in coffee can vary greatly from cup to cup or even brew method,” says Joy Alisa Maraj, RD, CNSC, clinical dietitian at Montefiore Medical Center Wakefield Campus in The Bronx, New York. Different beans, brands, and preparations all determine how much caffeine ends up in any one cup of coffee. For example, let’s say you get the same exact brew from the same location every single day. You could end up with varying amounts of caffeine in each cup if your barista puts a different amount of grounds in the coffee machine.
According to the USDA, the average 8-ounce cup of brewed coffee contains 95 milligrams of caffeine. But, a 2014 study published in the journal Food and Chemical Toxicology found that an 8-ounce cup of brewed coffee may contain anywhere from 75 to 165 milligrams of caffeine. Specialty coffees—think: Latte, mocha, cappuccino or Americano—were found to have 63 to 126 milligrams per 8-ounce serving. Though, again, most people probably aren’t getting specialty drinks this small (a Starbucks Tall is 12 ounces). Espresso can have as much as 500 milligrams of caffeine per 8-ounce serving, but one shot is just one ounce (which comes to about 63 milligrams per actual serving).
Photoboyko/Getty ImagesCaffeine sensitivity
“There is wide variation in how sensitive people are to the effects of caffeine,” says Nasrallah. For some people, even one cup of regular coffee a day can cause uncomfortable effects like restlessness, jitteriness, nervousness, and sleep interruptions. On the other side of the spectrum, some people may tolerate well over the recommended limit, feeling no adverse effects, says Mary M. Sweeney, MS, PhD, assistant professor in the Behavioral Pharmacology Research Unit of the Department of Psychiatry and Behavioral Sciences at Johns Hopkins School of Medicine in Baltimore.
“There are many factors that may contribute to individual differences in caffeine response,” Sweeney adds. “For example, people may have genetic differences that result in variations in the liver enzyme systems responsible for metabolizing, or breaking down, caffeine in the body. As a result, caffeine may be metabolized more quickly by some people than others, meaning it has less of a chance to linger in the body and cause pharmacological effects.”
Lifestyle factors and caffeine tolerance
In addition to genetic differences, people who consume caffeine often will build up a tolerance to the effects. Typical doses may begin to stop causing any adverse effects because the body makes adjustments with consistent exposure, Sweeney says. Over time, you may need higher amounts of caffeine to feel like it’s impacting you in any significant way.
Smoking cigarettes may also make you less sensitive to caffeine. “Cigarette smoking induces the production of liver enzymes that break down caffeine, meaning that cigarette smokers metabolize caffeine more quickly and may require more to feel its effects,” adds Sweeney.
anilakkus/Getty ImagesHealth conditions, medications, and caffeine
Caffeine temporarily raises heart rate and blood pressure, so high amounts can pose a risk for people with heart disease, says Nasrallah. Specifically, “individuals with atrial fibrillation and hypertension can experience symptoms like increased blood pressure and irregular heartbeat,” adds Maraj.
Sticking to beverages with low amounts of caffeine is also important for people with anxiety, sleep disorders, migraines, or gastroesophageal reflux disease (GERD), says Nasrallah. In all of these cases, caffeine can potentially exacerbate symptoms.
Some medications interact adversely with caffeine—either because the drug messes with caffeine metabolism or the caffeine messes with the drug metabolism. Also, people taking those medications should avoid caffeine-containing products, including coffee, says Nasrallah. For example, in a small study, published in Thyroid, researchers found taking a thyroid drug with coffee or espresso reduced the drug’s absorption rate. Always talk to your doctor to find out if it’s safe to combine caffeine with your prescription medication.
Pregnancy and caffeine intake
“It is crucial to curb your intake of caffeine if you are pregnant since it passes through the placenta to your baby,” says Nasrallah. According to the National Library of Medicine’s Drugs and Lactation Database, caffeine is metabolized more slowly in pregnant women. This means women may be noticeably more sensitive during pregnancy. There’s also no good scientific confirmation on what exact amount is safe for the baby.
Some studies, including one published in the American Journal of Obstetrics & Gynecology, have connected excess caffeine consumption during pregnancy to an increased risk of miscarriage. Other studies have found no connection. Until we have more definitive evidence, the American College of Obstetricians and Gynecologists suggests erring on the side of caution and limiting caffeine intake to 200 milligrams per day. Of course, it’s important to talk to your doctor to ensure your caffeine consumption is OK for you and your baby.
Breastfeeding mothers may also need to keep caffeine consumption low since it can be passed along to babies through breast milk, adds Nasrallah. Again, the best limit is unclear. But, the Drugs and Lactation Database notes that very high intakes (10 or more cups of coffee daily) has been shown to have negative impacts on the baby. Meanwhile, five cups of coffee daily showed no stimulation in breastfed infants 3 weeks of age or older. Preterm and very young infants may be more sensitive to caffeine in breast milk.
EvilWata/Getty ImagesOverdoing it on caffeine
“It is unlikely that someone could consume enough coffee to create a medical emergency,” says Sweeney. “This is more likely to occur with caffeine pills, caffeine-containing supplements or caffeine powders, or high-caffeine energy drinks where the amount of caffeine is more concentrated and easier to consume too much.”
For some context, the National Library of Medicine notes that lethal doses of caffeine are rare, and are commonly caused by intentional drug overdosing and/or connected to energy drinks and other OTC drugs loaded with caffeine. Deaths have been reported with blood concentrations that would be achieved by ingesting approximately 10 grams or greater. With a 12-ounce cup of brewed coffee containing approximately 200 milligrams, chances are you could never ingest that much caffeine from coffee alone even if you tried.
How caffeine is too much: The verdict
To gauge how much coffee is too much is simple. Especially, if you don’t have a health condition or take medication that shouldn’t be combined with caffeine. Paying attention to how caffeine makes you feel is a great way to know how much is too much.
“If you notice any changes in your mood or new/unusual bodily symptoms such as increased anxiousness, shakiness, headaches or heart palpitations/chest pains, these could be related to drinking too much coffee,” says Maraj. “Some people can also experience insomnia or poor sleep quality” when too much caffeine is messing with their body clock.
But if you aren’t experiencing adverse effects? You’re probably doing just fine. “If a person is not experiencing adverse effects of caffeine, does not have any problems with their pattern of consumption, and does not have any contraindications to caffeine consumption, I do not see a reason why they should stop,” says Sweeney.