What Happens to Your Body When You Drink Coffee During Your Menstrual Cycle

There are a lot of conflicting opinions out there about how the body reacts to coffee—particularly when it comes to one's menstrual cycle. Coffee (or, more acutely, the caffeine in coffee) has been claimed by experts to cause negative side effects during one's period, intensifying premenstrual syndrome (PMS) symptoms and breast tenderness. These claims come from an observational study published decades ago, as well as a previous study linking how moderate caffeine intake could affect a woman's estrogen levels—although the research is still up in the air.

So what is the truth? Can drinking coffee actually make your period last longer and make PMS symptoms worse? We asked women's health dietitian and expert Elizabeth Ward, MS, RDN whether drinking coffee could affect your menstrual cycle, and if there is any science to back up claims that it could make your PMS symptoms worse. Spoiler alert—it doesn't.

How Much Coffee Is Too Much?

The U.S. Food and Drug Administration (FDA) states that consumers should keep their caffeine intake at 400 milligrams a day. A cup of regular coffee averages around 100 milligrams per 8 ounces, meaning a coffee drinker should not have over 28 ounces (or four cups) of coffee in a day.

Nevertheless, if one drinks more than that allotted amount of caffeine in a day, there is a chance they could experience caffeine toxicity—aka, drinking too much caffeine at once. Experts say overconsumption of caffeine can even be lethal. Symptoms of caffeine overdose include:

• Trouble breathing
• Agitation and anxiety
• Irregular heartbeat
• Nausea or vomiting
• Dizziness
• Fever
• Diarrhea
• Convulsions/seizures
• Muscle twitching
• Increased thirst
• Increased urination

Coffee drinkers may also experience withdrawal symptoms after consuming caffeine such as headaches, drowsiness, irritability, nausea, and trouble concentrating.

What Happens When You Drink Coffee During Your Period

Your PMS Symptoms Will Remain the Same

Despite any previous claim you have seen online about drinking coffee during your period, no concrete evidence links caffeine intake with intensified PMS symptoms during your cycle.

"I think it's safe to say that there isn't much evidence that caffeine affects the menstrual cycle," says Ward.

She points to a 2016 prospective study published in the American Journal of Clinical Nutrition that further proves that caffeine intake is not associated with PMS symptoms and that there is no need to avoid it during one's cycle. The study came to this conclusion by evaluating the association between total caffeine, coffee, and tea intake and the development of PMS in a case-control study within the prospective Nurses' Health Study II. After weighing certain factors like age and smoking, the study was unable to make any link between consumption and PMS symptoms.

"That said, people vary in their reaction to caffeine," Ward warns. "Habitual 'users'—people who consume the same, reasonable amount (400 milligrams) on a regular basis will likely feel no effects of caffeine on their menstrual cycle."

The Length of your Period Will Remain the Same, or Could Even Be Shorter

Despite a previous observational study in the late 1990s that stated how caffeine could affect the timeframe of one's cycle, a recent 2022 cross-sectional study published in BMC Women's Health actually claimed the opposite. After evaluating 9,335 premenopausal women between the ages 25 and 45, researchers stated that coffee drinkers were less likely to experience longer menstrual cycles. Meaning that drinking their coffee had no effect on the length of one's cycle, or could even make the duration shorter.

Ward does make it clear that both of these referenced studies are observational, and more research needs to be done in order to determine how coffee could ultimately affect the length of one's cycle. Needless to say, there isn't enough evidence to show that it could make your period cycle longer.

Too Much Caffeine Could Intensify Menstrual Discomforts

Although the studies do not link caffeine intake and menstrual cycles, Ward points out that drinking too much caffeine could intensify some of the discomforts you may experience during your cycle already.

"Too much caffeine can intensify menstrual discomforts by making you jittery, causing problems sleeping, increased heart rate, and diarrhea," says Ward. "Caffeinated beverages such as coffee can increase acidity in your stomach, too."

However, if you keep to the allotted 400 milligrams of caffeine (or 28 ounces of coffee) during the day, caffeine should not bother your typical cycle. Ward even points out the beneficial ways caffeine gives you an extra boost of energy if you are prone to experience period fatigue during your cycle.

The Bottom Line

There isn't enough evidence to link how drinking coffee could affect one's menstrual cycle. While there is an observational study that shows how caffeine intake (whether it be coffee, tea, or another source) could be linked to shorter menstrual cycle durations, there is no concrete research to claim that caffeine in coffee can intensify PMS symptoms during one's period. However, if coffee already causes discomfort for a consumer, experts say that those comforts could intensify if the consumer is also going through their time of the month.