7 Surprising Signs You're Sensitive To Caffeine

Is it time to break up with your a.m. coffee?

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A woman has coffee while sitting in her living room. Experts explain symptoms of caffeine sensitivit...
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So many folks (like, literally millions) reach for a caffeinated beverage in the morning in order to wake up and feel alert. And many more drink coffees, teas, and energy drinks as the day goes on in order to stay awake. But what are the signs you are sensitive to caffeine?

If you have a caffeine sensitivity, even a small amount of the stuff can make you feel downright bizarre, often leading to symptoms that run the gamut from a pounding heart, to headaches, to feelings of anxiety. "The average person can take in about 200 to 400mg of caffeine and experience no side effects and fall asleep without difficulty at bedtime," Dr. Alexea M. Gaffney-Adams, M.D., a general infectious disease specialist, tells Bustle. "An individual with caffeine sensitivity will experience [some of the symptoms listed below] or caffeine overdose symptoms with ingestion of as little as 100mg of caffeine."

So, what causes it? "There are several reasons it could happen," says Ginger Hultin, MS, RDN, a Seattle-based registered dietitian and nutritionist. "One is the way that caffeine affects the brain. There are several gene variants that affect the way the liver metabolizes caffeine, which may impact how people respond to [it] ... There are also genes that increase the predisposition for high blood pressure when caffeine is regularly consumed, and about 9% of that population has that."

If you've got a caffeine intolerance, you'll know. After consuming it, and for hours afterward, you might notice a few (or all) of the symptoms below. If you do, and they're bothering you, it may be time to get through your day without coffee, and talk to your doctor about a possible sensitivity to caffeine.


You Feel Hot Or Your Face Flushes

Regardless of the temperature of the coffee, many people who are sensitive to caffeine feel hot or "flushed" after drinking it. "They may feel hot or even start sweating," Hultin says. "Caffeine sensitivity can be caused by the way caffeine affects the brain so this may be one reason this occurs."


You Really, Really Have To Pee

Caffeine can also affect sensitive people's GI tract, causing some rather unpleasant side effects. "People who are caffeine sensitive may notice stomach upset when they drink caffeine while others may notice diarrhea," Hutlin says. "Studies are mixed on why this happens — whether it may be a shift in hormones when caffeine is consumed, or other compounds in coffee could stimulate the bowels."

Some folks also notice an increased need to pee. "Increased urination is another symptom of caffeine-intolerant people because caffeine is a natural diuretic," she says. "Some people experience more urgency than others."


You Can Literally Feel Your Heart Pounding In Your Chest

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If you're suddenly wildly aware of your heart pounding away after drinking a cup of coffee, there's a good chance you're sensitive to caffeine. "Caffeine-sensitive individuals may experience palpitations which presents as racing of the heart or an irregular heartbeat," says Gaffney-Adams. "It can exacerbate abnormal heart rhythms such as atrial fibrillation (A-fib) or tachycardias (abnormally fast heart rhythms). This can be accompanied by a rise in blood pressure, which is also a result of caffeine sensitivity."

Any change in your heart rhythm warrants a trip to your doctor. If it turns out you are caffeine sensitive, they may have you cut back on your coffee intake, or suggest you switch to decaf.


You're Restless In Bed At Night

While others need coffee in order to feel peppy, even a few sips of coffee can cause you to feel a little too peppy. For example, caffeine can exacerbate restless leg syndrome, according to Gaffney-Adams. "The urge to move the legs as well spontaneous jerking leg movements accompanying this syndrome are increased." This normally happens when you're lying in bed at night, and can even happen hours after drinking coffee.

Restless leg syndrome can certainly keep you up, but so can the caffeine itself. "People who are sensitive may also notice that they have trouble sleeping because of caffeine, even if it is separated by many hours in the day," Hultin says. Cue hours of insomnia.


You Feel "Jittery" Or Have Muscle Spasms

The jitters might also play out in the form of muscles spasms. "It can cause twitching through increased muscle activity," Gaffney-Adams says. "This can be felt as well as observed as tremors and often accompanies anxiety associated with caffeine intake." Think eye spasms, shaky hands, and the inability to stop tapping your foot.


You Get Super Anxious Or Stressed

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Speaking of anxiety, feelings of stress and overwhelm can also increase right after consuming caffeine. "Caffeine increases ​stimulation in the adrenal glands and ​can ​amplify stress levels throughout the day," health coach Maranda Elkin tells Bustle. "This can elevate one's perception of stress​ and cause you to overreact in certain situations." You might, for example, feel totally overwhelmed when the phone rings, instead of answering it calmly like you usually do.


You Feel A Bit Uneasy

If you're intolerant of caffeine, Hutlin says you might "develop an uneasy, nervous feeling" after drinking caffeine due to the way it affects your brain. Referred to as derealization, this side effect can make you feel a bit disassociated, and usually happens after drinking large amounts of coffee. But it can happen in smaller doses for sensitive people, too.

So if that's the case, you might want to decrease your caffeine intake, to see if that helps. While most people don't experience unpleasant side effects after drinking coffee, these symptoms might indicate that you're sensitive to caffeine, and need to cut back.

Studies referenced:

Boekema, P. (1999). Coffee and gastrointestinal function: facts and fiction. A review. Scand J Gastroenterol Suppl.

De Giuseppe, R. (2019). Caffeine and blood pressure: a critical review perspective. Nutr Res Rev.

Kim, T-W. (2011). Caffeine increases sweating sensitivity via changes in sudomotor activity during physical loading. J Med Food.

Lovallo, W. (2005). Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels. Psychosom Med.

Lutz, E.G. (1978). Restless legs, anxiety and caffeinism. J Clin Psychiatry.

Molema, M. (2007). Caffeine and Muscle Cramps: A Stimulating Connection. The American Journal of Medicine.

Papakonstantinou, E. (2016). Acute effects of coffee consumption on self-reported gastrointestinal symptoms, blood pressure and stress indices in healthy individuals. Nutrition Journal.

Planning Committee for a Workshop on Potential Health Hazards Associated with Consumption of Caffeine in Food and Dietary Supplements; Food and Nutrition Board; Board on Health Sciences Policy; Institute of Medicine. Caffeine in Food and Dietary Supplements: Examining Safety: Workshop Summary. Washington (DC): National Academies Press (US); 2014 Apr 23. 5, Caffeine Effects on the Cardiovascular System. Available from:

Richards, G. (2015). Caffeine consumption and self-assessed stress, anxiety, and depression in secondary school children. Journal of Psychopharmacology.


Dr. Alexea M. Gaffney-Adams, M.D., a general infectious disease specialist

Ginger Hultin, MS, RDN, a Seattle-based registered dietitian and nutritionist

Maranda Elkin, health coach

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