Caffeine is a chemical found in coffee, tea, cola, guarana, mate, and other products.

Caffeine is most commonly used to improve mental alertness, but it has many other uses. Caffeine is used by mouth or rectally in combination with painkillers (such as aspirin and acetaminophen) and a chemical called ergotamine for treating migraine headaches. It is also used with painkillers for simple headaches and preventing and treating headaches after epidural anesthesia.

Some people use caffeine by mouth for asthma, gallbladder disease, attention deficit-hyperactivity disorder (ADHD), and many other conditions, but there is no good scientific evidence to support most of these uses.

Caffeine is one of the most commonly used stimulants among athletes. Taking caffeine, within limits, is allowed by the National Collegiate Athletic Association (NCAA). Urine concentrations over 15 mcg/mL are prohibited. It takes most people about 8 cups of coffee providing 100 mg/cup to reach this urine concentration.

Some caffeine products are sold in very concentrated or pure forms. These products are a health concern. People can easily use these products in doses that are much too high by mistake. This can lead to death. As of 2018, the U.S. Food and Drug Administration (FDA) considers it unlawful for these products to be sold to consumers in bulk.

In foods, caffeine is used as an ingredient in soft drinks, energy drinks, and other beverages.

People with voice disorders, singers, and other voice professionals are often advised against using caffeine. However, until recently, this recommendation was based only on hearsay. Now developing research seems to indicate that caffeine may actually harm voice quality. But further study is necessary to confirm these early findings.


Is a Form of:


Primary Functions:

Asthma, gallbladder disease

Also Known As:

1,3,7-Trimethyl-1H-purine- 2,6(3H,7H)-dione, 1,3,7-trimethylxanthine

How Does It Work?

Caffeine works by stimulating the central nervous system (CNS), heart, muscles, and the centers that control blood pressure. Caffeine can raise blood pressure, but might not have this effect in people who use it all the time. Caffeine can also act like a “water pill” that increases urine flow. But again, it may not have this effect in people who use caffeine regularly. Also, drinking caffeine during moderate exercise is not likely to cause dehydration.


  • Migraine. Taking caffeine by mouth together with pain relievers such aspirin and acetaminophen is effective for treating migraines. Caffeine is an FDA-approved product for use with pain relievers for treating migraine headaches.
  • Pauses in breathing that may be followed by low heart rate and low oxygen levels in newborns. "Neonatal apnea" describes a condition in which infants have pauses in breathing that last for at least 15 seconds or that cause a serious drop in heart rate. This condition is common in very premature infants. Caffeine given by mouth or intravenously (by IV) can improve breathing in very premature infants with this condition. It also seems to reduce the number of episodes of apnea by at least half over 7-10 days. Caffeine citrate is approved as a prescription drug for treating neonatal apnea in premature infants. But caffeine does not seem to prevent this condition from developing in premature infants.
  • Headache after surgery. Using caffeine by mouth or intravenously is effective for preventing headaches following surgery. Caffeine is an FDA-approved product for this use in people who regularly consume products that contain caffeine.
  • Tension headache. Taking caffeine by mouth in combination with pain relievers is effective for treating tension headaches.
  • Mental alertness.Research suggests that drinking caffeinated beverages throughout the day keeps the mind alert and might improve reaction times. Combining caffeine with glucose as an "energy drink" seems to improve mental performance better than either caffeine or glucose alone.
  • Decline in memory and thinking skills that occurs normally with age. Postmenopausal women who consume more than 175-371 mg of caffeine daily seem to have a lower risk of mental decline compared to those who consume less caffeine. There is some evidence that drinking caffeinated coffee but not caffeinated tea is linked to slower mental decline. But other research did not find a difference between caffeinated products.
  • Asthma. Caffeine appears to improve airway function for up to 4 hours in people with asthma.
  • Athletic performance. Taking caffeine seems to increase physical strength and endurance and might delay exhaustion during exercise. It might also reduce feelings of exertion and improve performance during activities such as cycling, running, playing soccer, and golfing. But caffeine doesn't seem to improve performance during short-term, high-intensity exercise such as sprinting and lifting. The dose of caffeine doesn't seem to impact its effect on athletic performance, but the timing might. Caffeine might work better during morning exercise than evening exercise. Also, taking caffeine daily for up to 4 weeks might also lead to tolerance. This might decrease or eliminate any performance enhancing effects of caffeine. The variability in the effects of caffeine might be due to genetic differences between people.
  • Diabetes. Drinking beverages that contain caffeine is linked with a lower risk of developing type 2 diabetes. It appears that the more caffeine that is consumed, the lower the risk. Although caffeine might help prevent type 2 diabetes, it might not be effective in treating type 2 diabetes. Research on the effects of caffeine in people with type 1 diabetes is inconsistent. Some research shows benefit, while other research does not.
  • Gallbladder disease. Drinking beverages that provide at least 400 mg of caffeine daily seems to reduce the risk of developing gallstone disease. The effect seems to be dose-dependent. Taking 800 mg of caffeine daily seems to work best.
  • Swelling (inflammation) of the liver caused by the hepatitis C virus (hepatitis C). Research has found that higher intake of caffeine from coffee is linked with reduced liver scarring in people with hepatitis C.
  • Low blood pressure. Drinking caffeinated beverages seems to increase blood pressure in older people with low blood pressure after eating.
  • Memory. Taking 200 mg of caffeine by mouth daily seems to improve memory in some people with outgoing personalities and college students.
  • Obesity. Taking caffeine in combination with ephedrine seems to help reduce weight, short-term. Taking 192 mg of caffeine in combination with 90 mg of ephedra daily for 6 months seems to cause a modest weight reduction (5.3 kg or about 12 pounds) in overweight people. This combination, along with limiting fat intake to 30 percent of calories and moderate exercise, also seems to reduce body fat, decrease "bad" low-density lipoprotein (LDL) cholesterol, and increase "good" high-density lipoprotein (HDL) cholesterol. However, there can be unwanted side effects. Even in carefully screened and monitored otherwise healthy adults, caffeine/ephedra combinations can cause changes in blood pressure and heart rate. Early research shows that taking a specific combination product (Prograde Metabolism) along with dieting reduces body weight and the size of the waist and hips.
  • Pain. Research suggests that taking caffeine together with painkillers can reduce pain.
  • Parkinson disease. Some research suggests that people who drink caffeinated beverages have a decreased risk of developing this condition. But this reduced risk is not observed in people who smoke cigarettes.
  • Headache after epidural anesthesia. Taking caffeine by mouth or intravenously seems to help prevent headache after epidural anesthesia.
  • Skin cancer. Research has found that higher intake of caffeine is linked with a reduced risk for developing a certain type of skin cancer, called non-melanoma skin cancer.

Recommended Dosing

The following doses have been studied in scientific research:



  • General: One cup of brewed coffee provides from 95-200 mg of caffeine. An 8-ounce serving of black tea provides from 40-120 mg of caffeine. An 8-ounce serving of green tea provides 15-60 mg of caffeine. Soft drinks such as cola provide from 20-80 mg of caffeine per 12 ounce serving. Sports or energy drinks typically provide from 48-300 mg of caffeine per serving.
  • For headache: Does of 100-250 mg caffeine daily have been used. Caffeine has also been used together with acetaminophen, aspirin, ergotamine, and sumatriptan.
  • For headache after epidural anesthesia: Caffeine 300 mg has been used.
  • For mental alertness: Doses of 100-600 mg caffeine daily have been used. Caffeine has also been taken together with taurine, glucose and L-theanine.
  • For asthma: Caffeine has been taken in doses of 9 mg/kg.
  • For improving athletic performance: 2-10 mg/kg has been used. Keep in mind that doses in excess of 800 mg per day can result in urine levels greater than the 15 mcg/mL allowed by the National Collegiate Athletic Association.
  • For preventing gallstone disease: Consumption of 400 mg or more of caffeine daily has been used.
  • For memory: 65-200 mg of caffeine has been used.
  • For obesity: Ephedrine/caffeine combination products are commonly dosed 20 mg/200 mg three times daily. A specific combination product (Prograde Metabolism) containing 1000 mg of a combination of raspberry ketone, caffeine, capsicum extract, garlic root extract, ginger root extract, bitter orange fruit, L-theanine, and black pepper fruit extract has been used twice daily for 8 weeks.
  • For pain: Doses of 50-130 mg caffeine have been used with pain relievers including acetaminophen, propyphenazone, and ibuprofen.
  • For preventing Parkinson disease: Men drinking 421-2716 mg of total caffeine daily have the lowest risk of developing Parkinson disease, when compared to other men. However, men who drink as little as 124-208 mg of caffeine daily also have a significantly lower chance of developing Parkinson disease. In women, moderate caffeine intake per day (1-3 cups of coffee per day) seems to be best.


  • Headache after surgery: 200 mg of caffeine has been given intravenously to prevent headache after surgery.



  • For breathing problems in premature infants (neonatal apnea): Caffeine is given by mouth to infants by healthcare providers for this condition.


  • For a lung disease that affects newborns (bronchopulmonary dysplasia): Caffeine is given intravenously (by IV) by healthcare providers for this condition.
  • For headache after epidural anesthesia: Caffeine is given intravenously (by IV) by healthcare providers for this condition.

Caffeine Supplements Frequently Asked Questions

Is it safe to take 200mg of caffeine?

Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks.

Do caffeine pills help you lose weight?

Caffeine is a well known metabolism booster, and is often added to commercial weight loss supplements. How it works: Short-term studies have shown that caffeine can boost metabolism by 3-11%, and increase fat burning by up to 29% ( 7 , 8 , 9, 10).

Are caffeine drinks bad for you?

“Young people suffering with eating disorders often use low calorie energy drinks to boost energy levels with the caffeine they contain whilst limiting calories,” Thornton-Wood adds. “These individuals are at greater risk of heart arrhythmias from the high doses of caffeine.”

Do caffeine pills have side effects?

Caffeine is POSSIBLY UNSAFE when taken by mouth for a long time or in high doses (>400 mg per day). Caffeine can cause insomnia, nervousness and restlessness, stomach irritation, nausea and vomiting, increased heart rate and respiration, and other side effects.

Can I take caffeine everyday?

Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks.

Is 200mg of caffeine a lot?

Studies show that 100 to 200 mg of caffeine (about 1 to 2 cups of regular coffee) are enough to achieve these results. When caffeine consumption climbs to 250 to 700 mg per day, people may experience nausea, headaches, sleep difficulties or increased anxiety.  For now, you should stick to moderate amounts of caffeine.

How long do caffeine pills take to kick in?

It can take about an hour for caffeine pills to be fully absorbed in the bloodstream and take full effect. Depending on body composition, it can take anywhere between 3 and 12 hours for the body to metabolize half of the caffeine present.

Is caffeine bad for your kidneys?

Caffeine causes a short but sudden increase in blood pressure. Research has not shown that drinking 3-4 cups of coffee a day increases the risk of kidney disease or increases rate of decline of kidney function. Those struggling with blood pressure control should especially drink less than three cups per day.

Do caffeine pills work like Adderall?

Some studies have found that caffeine can boost concentration for people with ADHD. Since it's a stimulant drug, it mimics some of the effects of stronger stimulants used to treat ADHD, such as amphetamine medications. However, caffeine alone is less effective than prescription medications.

Do caffeine pills really work?

Like drinking a cup of coffee, taking a caffeine pill can provide a temporary boost in energy, memory, and focus. While caffeine pills may help a person study or stay awake, high doses of caffeine can cause side effects and may not be safe for everyone.

How many caffeine pills can i take at once?

Up to 400 mg of caffeine per day (or about 2 caffeine pills) is generally deemed safe for most adults. Make sure to read the package to see how much caffeine a particular product contains, and then follow the directions.

Does caffeine make you gain weight?

Coffee alone does not cause weight gain — and may, in fact, promote weight loss by boosting metabolism and aiding appetite control. However, it can negatively affect sleep, which may promote weight gain. Additionally, many coffee drinks and popular coffee pairings are high in calories and added sugar.

How much caffeine should you have in the morning?

SUMMARY The caffeine content of your morning joe can range from 50 to over 400 mg. Many sources recommend 400 mg of caffeine per day as the safe upper limit for healthy adults.

Does caffeine keep you awake?

Because caffeine is a stimulant, most people use it after waking up in the morning or to remain alert during the day. While it is important to note that caffeine cannot replace sleep, it can temporarily make us feel more alert by blocking sleep-inducing chemicals in the brain and increasing adrenaline production.

Is caffeine hard on your liver?

While coffee is bad for some people's hearts, new research shows that four cups of coffee or tea a day may be good for your liver. Researchers found that caffeine helps the body break up fat stored in liver cells, which prompted them to believe caffeine-based medications may help certain people with the disease.

Is 25 mg of caffeine a lot?

How much is too much? Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks.

Is it bad to mix caffeine and Adderall?

Although ingesting a small amount of caffeine with Adderall is unlikely to be harmful, mixing these two stimulant drugs is not a good idea. If you or your child has a prescription for Adderall, it's best to limit your caffeine intake, as it will intensify unpleasant side effects.

Do caffeine pills help you focus?

Like drinking a cup of coffee, taking a caffeine pill can provide a temporary boost in energy, memory, and focus. While caffeine pills may help a person study or stay awake, high doses of caffeine can cause side effects and may not be safe for everyone.

Is 1000 mg of caffeine too much?

250–300 mg of caffeine a day is a moderate amount. That is as much caffeine that is in three cups of coffee (8oz each cup). More than 750–1000 mg a day is a significant amount, but is very unlikely to kill someone. ... Decaffeinated coffee (with most caffeine taken out) - 3 to 5 mg in a cup.

Clinical Studies