Guarana: MedlinePlus Supplements

T What is it?
P Guarana is a plant. It is named for the Guarani tribe in the Amazon, who used its seeds to brew a drink. Today, guarana seeds are still used as medicine.
P People take guarana for weight loss, athletic performance, mental performance, to increase energy, as an aphrodisiac, and for many other conditions, but there is no good scientific evidence to support these uses. Guarana can also be unsafe when taken long-term in large amounts.

T How effective is it?
P Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
P The effectiveness ratings for GUARANA are as follows:
t Insufficient evidence to rate effectiveness for...
- Anxiety. Early research shows that taking a product containing hawthorn, black horehound, passionflower, valerian, cola nut, and guarana can reduce anxiety in some people. It is not clear if guarana alone is beneficial.
- Lack of appetite in patients with cancer. Early research shows that taking guarana extract slightly improves appetite and prevents weight loss in people with cancer who have lost their appetite and are losing weight. But the benefit is very small.
- Chemotherapy-related fatigue. Some research shows that taking guarana can reduce feelings of tiredness in some people undergoing chemotherapy. But conflicting results exist.
- Mental performance. Early research in healthy people shows that taking a single dose of guarana extract can improve thinking speed and some aspects of memory. However, other research shows that taking guarana does not improve mental function in adults or older people.
- Exercise tolerance. Research shows that taking a single dose of a product containing guarana, B vitamins, vitamin C, and minerals improves exercise tolerance in trained athletes by a very small amount. It is not clear if guarana alone is beneficial.
- Weight loss. Taking guarana along with mate and damiana seems to increase weight loss. There is also developing evidence that taking a specific combination product containing guarana, ephedra, and 17 other vitamins, minerals, and supplements helps reduce weight by approximately 2.7 kg over 8 weeks when used with a low-fat diet and exercise. It is not clear if guarana alone is beneficial.
- Feelings of well-being. Early research shows that taking guarana does not improve feelings of mood in healthy individuals.
- Radiation sickness. Research shows that taking guarana does not improve symptoms of depression or tiredness in people undergoing radiation treatment.
- Chronic fatigue syndrome (CFS). word
- Diarrhea. word
- Fever. word
- Fluid retention. word
- Headaches.
- Heart problems.
- Improvement of exercise endurance.
- Improvement of short-term, high-intensity performance and power.
- Increasing blood pressure in people who have low blood pressure.
- Joint pain.
- Malaria.
- Other conditions.
P More evidence is needed to rate guarana for these uses.

T How does it work?
P Guarana contains caffeine. Caffeine works by stimulating the central nervous system (CNS), heart, and muscles. Guarana also contains theophylline and theobromine, which are chemicals similar to caffeine.

T Are there safety concerns?
P Guarana is LIKELY SAFE for most adults when consumed in amounts commonly found in foods.
P Guarana is POSSIBLY SAFE when taken my mouth in medicinal amounts for a short time.
P Guarana is POSSIBLY UNSAFE when taking by mouth in high doses for a long time. Doses greater than 250-300 mg daily have been linked to side effects. Side effects depend on the dose. At typical doses, the caffeine in guarana can cause insomnia, nervousness and restlessness, stomach irritation, nausea, vomiting, increased heart rate and blood pressure, rapid breathing, tremors, delirium, diuresis, and other side effects. Large guarana doses might cause headache, anxiety, agitation, ringing in the ears, pain when urinating, stomach cramps, and irregular heartbeats. People who take guarana regularly may experience caffeine withdrawal symptoms if they reduce their usual amount.
P Guarana is LIKELY UNSAFE and even deadly, due to its caffeine content, when taken by mouth or injected in very high doses. The fatal dose of caffeine is estimated to be 10-14 grams (150-200 mg per kilogram; the "typical" man weighs about 70 kilograms, so a lethal dose of caffeine for this man would be 10,500-14,000 mg). This is quite a high dose. Consider that one cup of brewed coffee provides from 95-200 mg of caffeine. However, serious poisoning can occur at doses lower than 150-200 mg per kilogram depending on an individual's caffeine sensitivity or smoking behavior, age, and prior caffeine use.
t Special precautions & warnings:
P Pregnancy and breast-feeding: Guarana is POSSIBLY SAFE for pregnant and breast feeding women when taken in amounts commonly found in foods. If you are pregnant or breast-feeding, guarana should be taken with caution due to the caffeine content. Small amounts are probably not harmful. However, taking guarana in high doses by mouth is POSSIBLY UNSAFE. Consuming more than 200 mg has been linked to an increased risk of miscarriage and other negative effects.
P Anxiety: The caffeine in guarana might make feelings of anxiety worse.
P Bleeding disorders: There is some evidence suggesting that the caffeine in guarana might make bleeding disorders worse, although this has not been reported in people. If you have a bleeding disorder, check with your healthcare provider before starting guarana.
P Diabetes: Some research suggests that the caffeine in guarana may affect the way people with diabetes process sugar (glucose) and may complicate blood sugar control. There is also some interesting research that suggests caffeine may enhance the warning symptoms of low blood sugar in patients with type 1 diabetes. Some studies show that the symptoms of low blood sugar are more intense when they start in the absence of caffeine, but as low blood sugar continues, symptoms are greater with caffeine. This might increase the ability of diabetic patients to detect and treat low blood sugar. However, the downside is that caffeine might actually increase the number of low-sugar episodes. If you have diabetes, talk with your healthcare provider before starting guarana.
P Diarrhea. Guarana contains caffeine. The caffeine in guarana, especially when taken in large amounts, can worsen diarrhea.
P Seizures. Guarana contains caffeine. The caffeine in guarana might increase the risk of seizures and reduce the benefits of many medications used to control seizures. If you have seizures, talk to your healthcare provider before using guarana.
P Irritable bowel syndrome (IBS): Guarana contains caffeine. The caffeine in guarana, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
P Heart disease: The caffeine in guarana might cause irregular heartbeat in certain people. Use with caution.
P High blood pressure: Taking guarana might raise blood pressure in people with high blood pressure due to its caffeine content. However, this effect might be less in people who are regular coffee-drinkers or otherwise use caffeine on a regular basis.
P Glaucoma: The caffeine in guarana increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes after drinking caffeinated beverages.
P Bladder control problems (Incontinence): Guarana contains caffeine. The caffeine in guarana might reduce bladder control, especially in older women. If you need to urinate often with high urgency, use guarana cautiously.
P Osteoporosis: The caffeine in guarana can flush calcium out of the body through the kidneys. This calcium loss might help to weaken bones. To minimize this problem, don't use more than 300 mg of caffeine per day. Taking calcium supplements may also help to offset these calcium losses. Postmenopausal women who have a genetic problem that affects how vitamin D is used by the body should use caffeine with caution.
P Schizophrenia: Guarana contains caffeine. The caffeine in guarana might make some symptoms of schizophrenia worse. If you have schizophrenia, use guarana cautiously.

T Are there interactions with medications?
P Major
P Do not take this combination.
P Amphetamines
P Stimulant drugs such as amphetamines speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
P Cocaine
P Stimulant drugs such as cocaine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
P Ephedrine
P Stimulant drugs speed up the nervous system. Caffeine (contained in guarana) and ephedrine are both stimulant drugs. Taking guarana 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.
P Moderate
P Be cautious with this combination.
P Adenosine (Adenocard)
P Guarana contains caffeine. The caffeine in guarana might block the affects 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 guarana or other caffeine-containing products at least 24 hours before a cardiac stress test.
P Antibiotics (Quinolone antibiotics)
P 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 guarana can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.
P 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).
P CARBAMAZEPINE (Tegretol)
P Carbamazepine (Tegretol) is used to treat some seizures. Caffeine in guarana might lower the effects of carbamazepine (Tegretol) or increase how susceptible a person is to seizures. In theory, taking guarana with carbamazepine (Tegretol) might reduce its effects and increase the risk of seizures in some people.
P Cimetidine (Tagamet)
P Guarana contains 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 guarana might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.
P Clozapine (Clozaril)
P The body breaks down clozapine (Clozaril) to get rid of it. The caffeine in guarana seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking guarana along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).
P Dipyridamole (Persantine)
P Guarana contains caffeine. The caffeine in guarana might block the effects 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 guarana or other caffeine-containing products at least 24 hours before a cardiac stress test.
P Disulfiram (Antabuse)
P The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking guarana (which contains caffeine) along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.
P Estrogens
P The body breaks down the caffeine in guarana to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking guarana along with estrogens can cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogens, limit your caffeine intake.
P Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.
P Ethosuximide
P Ethnosuximide is used to control certain types of seizures. Caffeine in guarana might lower the effects of ethnosuximide or increase how susceptible a person is to seizures. In theory, taking guarana with ethnosuximide might reduce its effects and increase the risk of seizures.
P Felbamate
P Felbamate is used to control certain types of seizures. Caffeine in guarana might lower the effects of felbamate or increase how susceptible a person is to seizures. In theory, taking guarana with felbamate might reduce its effects and increase the risk of seizures.
P Flutamide (Eulexin)
P The body breaks down flutamide (Eulexin) to get rid of it. Caffeine in guarana might decrease how quickly the body breaks down flutamide (Eulexin). In theory, taking guarana along with flutamide (Eulexin) might cause too much flutamide (Eulexin) in the body and increase the risk of side effects.
P Fluvoxamine (Luvox)
P The body breaks down the caffeine in guarana to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking guarana along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.
P Lithium
P You body naturally gets rid of lithium. The caffeine in guarana 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.
P Medications for asthma (Beta-adrenergic agonists)
P Guarana contains caffeine. Caffeine can stimulate the heart. Some medications for asthma can also stimulate the heart. Taking caffeine with some medications for asthma might cause too much stimulation and cause heart problems.
P Some medications for asthma include albuterol (Proventil, Ventolin, Volmax), metaproterenol (Alupent), terbutaline (Bricanyl, Brethine), and isoproterenol (Isuprel).
P Medications for depression (MAOIs)
P Guarana contains caffeine. Caffeine can stimulate the body. Some medications used for depression can also stimulate the body. Taking guarana with these medications used for depression might cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others.
P Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.
P Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
P Guarana contains caffeine. Caffeine might slow blood clotting. Taking guarana along with medications that also slow clotting might increase the chances of bruising and bleeding.
P 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.
P Nicotine
P Stimulant drugs such as nicotine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
P Pentobarbital (Nembutal)
P The stimulant effects of the caffeine in guarana can block the sleep-producing effects of pentobarbital.
P Phenobarbital
P Phenobarbital is used to control some types of seizures. Caffeine, contained in guarana, might lower the effects of phenobarbital or increase how susceptible a person is to seizures. In theory, taking guarana with phenobarbital might reduce its effects and increase the risk of seizures.
P Phenylpropanolamine
P The caffeine in guarana can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking guarana along with phenylpropanolamine might cause too much stimulation and increase heartbeat, blood pressure and cause nervousness.
P Phenytoin
P Phenytoin is used to control some types of seizures. Caffeine in guarana might lower the effects of phenytoin or increase how susceptible a person is to seizures. In theory, taking guarana with phenytoin might reduce its effects and increase the risk of seizures.
P Riluzole (Rilutek)
P The body breaks down riluzole (Rilutek) to get rid of it. Taking guarana can decrease how fast the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole.
P Stimulant drugs
P Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heartbeat. Guarana contains caffeine, which can also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with guarana.
P Some stimulant drugs include nicotine, cocaine, sympathomimetic amines, and amphetamines.
P Theophylline
P Guarana contains caffeine. Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. Taking guarana along with theophylline might increase the effects and side effects of theophylline.
P Valproate
P Valproate is used to control some types of seizures. Caffeine in guarana might lower the effects of valproate or increase how susceptible a person is to seizures. In theory, taking guarana with valproate might reduce its effects and increase the risk of seizures.
P Verapamil (Calan, Covera, Isoptin, Verelan)
P The body breaks down the caffeine in guarana to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Taking guarana along with verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of caffeine side effects including jitteriness, headache, and an increased heartbeat.
P Water pills (Diuretic drugs)
P Guarana contains caffeine. Caffeine can reduce potassium levels. "Water pills" can also decrease potassium levels in the body. In theory, taking guarana with water pills might cause potassium levels to drop too low.
P Some "water pills" that can deplete potassium include chlorothiazide (Diuril), chlorthalidone (Thalitone), furosemide (Lasix), hydrochlorothiazide (HCTZ, HydroDiuril, Microzide), and others.
P Minor
P Be watchful with this combination.
P Alcohol
P The body breaks down the caffeine in guarana to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking guarana along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.
P Birth control pills (Contraceptive drugs)
P The body breaks down the caffeine in guarana to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking guarana along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.
P 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.
P Fluconazole (Diflucan)
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine Taking guarana along with fluconazole (Diflucan) might increase the risk of caffeine side effects such as nervousness, anxiety, and insomnia.
P Medications for diabetes (Antidiabetes drugs)
P Guarana might increase blood sugar. Diabetes medications are used to lower blood sugar. By increasing blood sugar, guarana might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
P 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.
P Medications that decrease the breakdown of other medications by the liver (Cytochrome P450 1A2 (CYP1A2) inhibitors)
P Guarana contains caffeine. Caffeine is changed and broken down by the liver. Some drugs decrease how quickly the liver changes and breaks down certain medications and supplements. Taking guarana along with these drugs might slow the breakdown of caffeine and increase caffeine levels.
P Some of these medications that affect the liver include fluvoxamine, mexiletine, clozapine, psoralens, furafylline, theophylline, idrocilamide, and others.
P Metformin
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Metformin can decrease how quickly the body breaks down caffeine. Taking metformin along with guarana might increase the effects and side effects of caffeine.
P Methoxsalen
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Methoxsalen can decrease how quickly the body breaks down caffeine. Taking methoxsalen along with guarana might increase the effects and side effects of caffeine.
P Mexiletine (Mexitil)
P Guarana contains 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 guarana might increase the caffeine effects and side effects of guarana.
P Phenothiazines
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Phenothiazines can decrease how quickly the body breaks down caffeine. Taking phenothiazines along with guarana might increase the effects and side effects of caffeine.
P Terbinafine (Lamisil)
P The body breaks down caffeine (contained in guarana) to get rid of it. Terbinafine (Lamisil) can decrease how fast the body gets rid of caffeine and increase the risk of side effects including jitteriness, headache, increased heartbeat, and other effects.
P Tiagbine
P Tiagabine is used to control some types of seizures. Caffeine in guarana does not seem to influence the effects of tiagabine. However, long-term caffeine use might increase blood levels of tiagabine. In theory, long-term use of guarana might have a similar effect.
P Ticlopidine (Ticlid)
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Ticlopidine (Ticlid) can decrease how fast the body gets rid of caffeine. In theory, taking guarana along with ticlopidine (Ticlid) might increase the risk of caffeine side effects.

T Are there interactions with herbs and supplements?
P Bitter orange
P Guarana contains caffeine. Taking bitter orange along with herbs that contain caffeine, such guarana, can increase blood pressure and heart rate in people who otherwise have normal blood pressure. This might increase the chance of developing problems with the heart and blood vessels.
P Caffeine-containing herbs and supplements
P Guarana contains caffeine. Taking it with other herbs and supplements that also contain caffeine can increase both the harmful and helpful effects of caffeine. Other natural products that contain caffeine include coffee, black tea, green tea, oolong tea, pu-erh tea, mate, and cola.
P Calcium
P High caffeine intake from foods, beverages, and herbs including guarana increases urinary calcium excretion.
P Creatine
P There is some concern that combining caffeine, ephedra, and creatine might increase the risk of serious side effects. There is a report of stroke in an athlete who took 6 grams of creatine monohydrate, 400-600 mg of caffeine, 40-60 mg of ephedra, and a variety of other supplements daily for 6 weeks. Caffeine might also decrease creatine's possible beneficial effects on athletic performance.
P Danshen
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Danshen might decrease how quickly the body breaks down caffeine. Using danshen with guarana might increase caffeine levels.
P Echinachea
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Echinacea might decrease how quickly the body breaks down caffeine. Using echinacea with guarana might increase caffeine levels.
P Ephedra (Ma huang)
P Ephedra is a stimulant. Guarana is a stimulant, due to it's caffeine content. Using ephedra along with guarana can cause too much stimulation in the body. One unpublished report linked jitteriness, high blood pressure, seizures, temporary loss of consciousness, and hospitalization requiring life support with the use of a combination ephedra and guarana (caffeine) product. Don't take guarana with ephedra or other stimulants.
P Herbs and supplements that slow blood clotting (Anticoagulant/Antiplatelet herbs and supplements
P Guarana seems to be able to slow blood clotting. Using it along with other herbs and supplements that also slow blood clotting might increase the risk of bleeding in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, and Panax ginseng.
P Kudzu
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Kudzu might decrease how quickly the body breaks down caffeine. Using kudzu with guarana might increase caffeine levels.
P Magnesium
P High caffeine intake from foods, beverages, and herbs including guarana increases urinary magnesium excretion.
P Melatonin
P Guarana contains caffeine. Taking caffeine along with melatonin can increase melatonin levels. In theory, taking guarana with melatonin might also increase melatonin levels.
P Red clover
P Guarana contains caffeine. The body breaks down caffeine to get rid of it. Taking red clover might decrease how quickly the body breaks down caffeine. In theory, taking red clover with guarana might increase caffeine levels.

T Are there interactions with foods?
P There are no known interactions with foods.

T What dose is used?
P The appropriate dose of guarana depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for guarana. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

T Other names
P Brazilian Cocoa, Cacao Brésilien, Guarana Seed Extract, Guaranine, Paullinia cupana, Paullinia sorbilis, Zoom.

T Methodology
P To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.

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