Overview

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.

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.

Uses & Effectiveness ?

Effective for

  • 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.

Likely Effective for

  • 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.

Possibly Effective for

  • Athletic performance. Taking caffeine seems to increase physical strength and endurance and might delay fatigue during exercise. It might also reduce feelings of tiredness 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 certain types of lifting. The dose of caffeine doesn't seem to matter, but the timing might. Caffeine might work better during morning exercise than evening exercise. Also, taking caffeine daily for up to 4 weeks might lead to tolerance. This might decrease or eliminate any performance enhancing effects of caffeine.
  • A lung disease that affects newborns (bronchopulmonary dysplasia). Caffeine given by mouth or intravenously (by IV) to premature infants seems to reduce the risk for this lung problem.
  • 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.
  • Memory. Taking 200 mg of caffeine by mouth daily seems to improve memory in college students or people with outgoing personalities.
  • 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.
  • Acute pain. Research suggests that taking caffeine together with painkillers can reduce pain better than those painkillers alone.
  • Headache after epidural anesthesia. Taking caffeine by mouth or intravenously seems to help prevent headache after epidural anesthesia.

Possibly Ineffective for

  • Irregular heartbeat (atrial fibrillation). Research suggests that taking caffeine during and after heart surgery does not reduce the risk for an irregular heart rhythm, called atrial fibrillation.
  • Attention deficit-hyperactivity disorder (ADHD). Most research suggests that caffeine does not reduce ADHD symptoms in children. The use of caffeine in adolescents and adults with ADHD has not been studied.

Insufficient Evidence for

  • Decline in memory and thinking skills that occurs normally with age. Postmenopausal women who consume more than 371 mg of caffeine daily seem to have a lower risk of mental decline. There is some evidence that drinking caffeinated coffee, but not caffeinated tea, is linked to slower mental decline.
  • Asthma. Caffeine appears to improve airway function for up to 4 hours in people with asthma.
  • Cancer pain. Early research shows that receiving 200 mg of caffeine intravenously once daily for 2 days might reduce pain in people with advanced cancer.
  • Diseases, such as Alzheimer disease, that interfere with thinking (dementia). Some research suggests that caffeine intake is linked with a reduced risk of dementia after menopause. In patients with dementia, caffeine intake might improve agitation.
  • Depression. Some research suggests that caffeine intake is linked with an increased occurrence of depression symptoms in children. However, other research suggests that caffeinated coffee intake is linked to a decreased occurrence of depression in adults.
  • Low levels of oxygen in the blood caused by exercise. Early research shows that taking caffeine may improve breathing during exercise, but does not affect blood levels of oxygen in athletes with low blood oxygen levels during exercise
  • Muscle soreness caused by exercise. Some early research suggests that taking moderate doses of caffeine can reduce muscle pain during exercise, while lower doses may not help.
  • Gallbladder disease. Drinking beverages that provide at least 400 mg of caffeine daily seems to reduce the risk of developing gallstones. 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.
  • Headaches that affect people while sleeping (hypnic headache). Some early evidence suggests that drinking a cup of coffee before bed or upon waking up might help alleviate pain associated with headaches that occur during sleep.
  • Low blood pressure. Drinking caffeinated beverages seems to increase blood pressure in older people who have low blood pressure after eating.
  • Leg pain during exercise due to poor blood flow (intermittent claudication). Taking a single 6 mg dose of caffeine by mouth seems to improve walking and muscle strength in people with aching and cramping due to narrowed or blocked arteries.
  • Liver disease. Research suggests that drinking coffee might reduce the risk for liver cirrhosis. However, it is unclear if this effect is due to caffeine or other components of coffee.
  • Excessive daytime sleepiness (narcolepsy). Taking caffeine in the mornings might reduce drowsiness but does not help people with this condition to react faster.
  • Reviving newborns that have stopped breathing. Very premature infants have trouble breathing on their own. They may require a machine called a ventilator to help them breathe. But ventilators can damage to the infant's lungs. So, infants who need a ventilator are "weaned" or taken off the ventilator as early as possible. Giving caffeine early to very premature infants does not allow them to be weaned from a ventilator faster than giving them caffeine right before being weaned.
  • Nonmelanoma skin cancer. A higher intake of caffeine is linked with a reduced risk for developing a certain type of skin cancer, called nonmelanoma skin cancer.
  • 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 seen in people who smoke cigarettes. Caffeine does not seem to reduce most symptoms of Parkinson disease.
  • Stroke. Research shows that increased caffeinated or decaffeinated coffee intake is linked to a decreased risk of stroke in women. However, it is not clear if the effect is due to caffeine.
  • To aid a procedure for mental disorders that passes small electric currents through the brain (Electroconvulsive therapy or ECT).
  • Skin irritation, redness, and itching.
  • Other conditions.
More evidence is needed to rate caffeine for these uses.

Side Effects

When taken by mouth: Caffeine is LIKELY SAFE for most healthy adults when used in doses up to 400 mg per day. This amount of caffeine is similar to what is found in about 4 cups of coffee.

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, increased heart rate and respiration, and other side effects. Larger doses might cause headache, anxiety, agitation, and chest pain.

Caffeine is LIKELY UNSAFE when taken by mouth in very high doses as it can cause irregular heartbeats and even death. Products with very concentrated or pure caffeine have a high risk of being used in doses that are too high. Avoid using these products.

Special Precautions and Warnings

Children: Caffeine is POSSIBLY SAFE when given by mouth or intravenously (by IV) to preterm infants under the advice and care of a healthcare professional. Caffeine is also POSSIBLY SAFE when used by children and adolescents in amounts commonly found in foods.

Pregnancy and breast-feeding: Caffeine is POSSIBLY SAFE in pregnant or breast-feeding women when used daily amounts of less than 300 mg. This is about the amount in about 3 cups of coffee. Consuming larger amounts during pregnancy or when breast-feeding is POSSIBLY UNSAFE. When consumed in larger amounts during pregnancy, caffeine might increase the chance of miscarriage and other problems. Also, caffeine can pass into breast milk, so nursing mothers should closely monitor caffeine intake to make sure it is on the low side. High intake of caffeine by nursing mothers can cause sleep disturbances, irritability, and increased bowel activity in breast-fed infants.

Anxiety disorders: Caffeine might make these conditions worse. Use with care.

Bipolar disorder: Too much caffeine might make this condition worse. In one case, a 36-year-old man with controlled bipolar disorder was hospitalized with symptoms of mania after drinking several cans of an energy drink containing caffeine, taurine, inositol, and other ingredients (Red Bull Energy Drink) over a period of 4 days. Use caffeine with care and in low amounts if you have bipolar disorder.

Bleeding disorders: There is concern that caffeine might aggravate bleeding disorders. Use caffeine with care if you have a bleeding disorder.

Heart conditions: Caffeine can cause irregular heartbeat in sensitive people. Use caffeine with caution.

Diabetes: Some research suggests that caffeine may affect the way the body uses sugar and might worsen diabetes. However, the effect of caffeinated beverages and supplements has not been studied. If you have diabetes, use caffeine with caution.

Diarrhea: Caffeine, especially when taken in large amounts, might worsen diarrhea.

Epilepsy: People with epilepsy should avoid using caffeine in high doses. Low doses of caffeine should be used cautiously.

Glaucoma: Caffeine increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes after drinking caffeinated beverages.

High blood pressure: Consuming caffeine might increase blood pressure in people with high blood pressure. However, this effect might be less in people who use caffeine regularly.

Loss of bladder control: Caffeine can make bladder control worse by increasing frequency of urination and the urge to urinate.

Irritable bowel syndrome (IBS): Caffeine, especially when taken in large amounts, might worsen diarrhea in people with IBS.

Weak bones (osteoporosis): Caffeine can increase the amount of calcium that is flushed out in the urine. If you have osteoporosis or low bone density, caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of coffee). It is also a good idea to get extra calcium to make up for the amount that may be lost in the urine. If you are generally healthy and getting enough calcium from your food or supplements, taking up to 400 mg of caffeine per day (3-5 cups of coffee) doesn't seem to increase the risk of getting osteoporosis. Older women with an inherited disorder that affects the way vitamin D is used should use caffeine with caution. Vitamin D works with calcium to build bones.

Parkinson disease: Taking caffeine with creatine might make Parkinson disease e get worse faster. If you have Parkinson disease and take creatine, use caffeine with caution.

Schizophrenia: Caffeine might worsen symptoms of schizophrenia.

Interactions ?

    Major Interaction

    Do not take this combination

  • Ephedrine interacts with CAFFEINE

    Stimulant drugs speed up the nervous system. Caffeine and ephedrine are both stimulant drugs. Taking caffeine along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine-containing products and ephedrine at the same time.

    Moderate Interaction

    Be cautious with this combination

  • Adenosine (Adenocard) interacts with CAFFEINE

    Caffeine might block the effects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming caffeine-containing products at least 24 hours before a cardiac stress test.

  • Antibiotics (Quinolone antibiotics) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with caffeine can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.

    Some antibiotics that decrease how quickly the body breaks down caffeine include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar).

  • Cimetidine (Tagamet) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with caffeine might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.

  • Clozapine (Clozaril) interacts with CAFFEINE

    The body breaks down clozapine (Clozaril) to get rid of it. Caffeine seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking caffeine along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).

  • Dipyridamole (Persantine) interacts with CAFFEINE

    Caffeine might block the affects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming caffeine-containing products at least 24 hours before a cardiac stress test.

  • Disulfiram (Antabuse) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking caffeine along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.

  • Estrogens interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking caffeine along with estrogens might cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogens limit your caffeine intake.

    Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

  • Fluvoxamine (Luvox) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking caffeine along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.

  • Lithium interacts with CAFFEINE

    You body naturally gets rid of lithium. Caffeine can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.

  • Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs) interacts with CAFFEINE

    Caffeine might slow blood clotting. Taking caffeine along with medications that also slow clotting might increase the chances of bruising and bleeding.

    Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.

  • Medications for depression (MAOIs) interacts with CAFFEINE

    Caffeine can stimulate the body. Some medications used for depression can also stimulate the body. Taking caffeine along with some medications for depression might cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others.

    Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.

  • Phenylpropanolamine interacts with CAFFEINE

    Caffeine can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking caffeine along with phenylpropanolamine might cause too much stimulation and increase heartbeat, blood pressure, and cause nervousness.

  • Pentobarbital (Nembutal) interacts with CAFFEINE

    The stimulant effects of caffeine can block the sleep-producing effects of pentobarbital.

  • Riluzole (Rilutek) interacts with CAFFEINE

    The body breaks down riluzole (Rilutek) to get rid of it. Taking caffeine along with riluzole (Rilutek) might decrease how fast the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole (Rilutek).

  • Stimulant drugs interacts with CAFFEINE

    Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heart rate. Caffeine might also speed up the nervous system. Taking caffeine along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.

    Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.

  • Theophylline interacts with CAFFEINE

    Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. Taking theophylline along with caffeine might increase the effects and side effects of theophylline.

  • Verapamil (Calan, Covera, Isoptin, Verelan) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Taking caffeine along with verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of side effects for caffeine including jitteriness, headache, and an increased heartbeat.

    Minor Interaction

    Be watchful with this combination

  • Alcohol interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking caffeine along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.

  • Birth control pills (Contraceptive drugs) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking caffeine along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.

    Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.

  • Fluconazole (Diflucan) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine. Taking caffeine along with fluconazole (Diflucan) might cause caffeine to stay in to body too long and increase the risk of side effects such as nervousness, anxiety, and insomnia.

  • Medications for diabetes (Antidiabetes drugs) interacts with CAFFEINE

    Caffeine might increase blood sugar. Diabetes medications are used to lower blood sugar. Taking some medications for diabetes along with caffeine might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

    Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

  • Mexiletine (Mexitil) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking Mexiletine (Mexitil) along with caffeine might increase the effects and side effects of caffeine.

  • Terbinafine (Lamisil) interacts with CAFFEINE

    The body breaks down caffeine to get rid of it. Terbinafine (Lamisil) can decrease how fast the body gets rid of caffeine. Taking caffeine along with terbinafine (Lamisil) can increase the risk of caffeine side effects including jitteriness, headache, increased heartbeat, and other effects.

Dosing

The following doses have been studied in scientific research:

ADULTS

BY MOUTH:
  • 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 migraine or tension 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 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 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 acute pain: Doses of 50-130 mg caffeine have been used with pain relievers including acetaminophen, propyphenazone, and ibuprofen.
BY IV:
  • For headache after surgery: 200 mg of caffeine has been given intravenously to prevent headache after surgery.
  • For headache after epidural anesthesia: Caffeine is given intravenously (by IV) by healthcare providers for this condition.
CHILDREN

BY MOUTH:
  • For pauses in breathing that may be followed by low heart rate and low oxygen levels in newborns: Caffeine is given by mouth to infants by healthcare providers for this condition.
View References

CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is provided by Natural Medicines Comprehensive Database Consumer Version. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version. © Therapeutic Research Faculty 2018.