• Caffeine is a natural stimulant most commonly found in tea, coffee, and cacao plants.It works by stimulating the brain and central nervous system, helping you stay alert and prevent the onset of tiredness.
• It functions by blocking the effects of adenosine, which is a neurotransmitter that relaxes the brain and makes you feel tired .
• Caffeine helps you stay awake by connecting to adenosine receptors in the brain without activating them. This blocks the effects of adenosine, leading to reduced tiredness.

Effective for

•  Migraine. Caffeine is an FDA-approved product for use with pain relievers for treating migraine headaches.
•  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..
•  Tension headache. Taking caffeine by mouth in combination with pain relievers is effective for treating tension headaches.

Likely Effective for

•  Mental alertness. Combining caffeine with glucose as an "energy drink" seems to improve mental   performance better than either caffeine or glucose alone. Possibly Effective for
•  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
•  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
•  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.
•  Low blood pressure. Drinking caffeinated beverages seems to increase blood pressure in older people with low blood   pressure after eating.
•  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.

• 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's 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.
• Caffeine can make sleep disorders in patients with acquired immunodeficiency syndrome (AIDS) worse. Larger doses might cause headache, anxiety, agitation, chest pain, and ringing in the ears.
• 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.
• 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.
• Bleeding disorders: There is concern that caffeine might aggravate bleeding
• disorders.
• Heart conditions: Caffeine can cause irregular heartbeat in sensitive people. 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.
• Schizophrenia: Caffeine might worsen symptoms of schizophrenia.