7 mins read

Overview: Caffeine is taken to improve alertness or help you stay awake. It is also used for a breathing problem in certain babies. Caffeine is found in many foods and drinks. It affects each person differently. Side effects may depend on the total amount of caffeine you get from things you eat and drink, as well as any supplements or medicines you take that have caffeine. Common side effects include nervousness, restlessness, nausea, and an increased heart rate. Too much caffeine can be harmful. Consider all sources of caffeine to make sure you are not getting too much. 

Uses

What is caffeine used for?

Caffeine is commonly taken for the following reasons.

  • To improve alertness or make you feel more awake when you feel tired or drowsy
  • Breathing pauses in certain premature newborns (apnea of prematurity)

These uses may vary depending on the specific caffeine product being taken or prescribed. 

Caffeine may also be used for other conditions as determined by your health care provider.

How does caffeine work (mechanism of action)?

Caffeine is a stimulant. It acts within the brain to increase alertness.

Caffeine seems to help reduce breathing pauses (apnea) in babies in a few ways. It may make the brain more sensitive to carbon dioxide. Carbon dioxide tells the body to take a breath. Caffeine also seems to improve the strength of the main breathing muscle (the diaphragm) and helps the body breathe more regularly.

How is caffeine supplied (dosage forms)?

Brands and other names

  • Cafcit
  • NoDoz
  • Stay Awake
  • Vivarin

Example dosage forms and strengths

  • 20 mg/mL oral solution
  • 100 mg, 200 mg oral tablets

How should I store caffeine?

Caffeine should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of caffeine?

The most common side effects of caffeine are listed below. Caffeine is usually well tolerated, but there is a lot of variability in how each person responds to it. Tell your health care provider if you have any of these side effects that bother you.

  • Trouble sleeping (especially if you take caffeine later in the day or close to bedtime)
  • Nervousness, restlessness, or irritability
  • Nausea or an upset stomach
  • Increased heart rate

There may be other side effects of caffeine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of caffeine?

While less common, the most serious side effects of caffeine are described below, along with what to do if they happen.

Severe Allergic Reactions. Caffeine may cause allergic reactions, which can be serious. Stop taking caffeine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Serious Gut Problem. Some premature babies taking caffeine have had necrotizing enterocolitis, which is a serious problem with the intestines. There can be a leak from the intestines to the belly, and possibly a serious infection. Necrotizing enterocolitis is rare but very serious, can lead to death, and may require surgery to treat it. Get help right away if your baby has any of the following symptoms.

  • Swollen or bloated stomach
  • Bloody poop
  • Vomiting
  • Trouble breathing
  • Slow heart rate
  • Seems sluggish

Warnings & Precautions

Who should not use caffeine?

Allergies to Ingredients. People who are allergic to any of the following should not take caffeine.

  • Cafcit
  • Caffeine
  • NoDoz
  • Stay Awake
  • Vivarin
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific caffeine products they stock.

What should I know about caffeine before using it?

If caffeine was prescribed to you by a health care provider, take it as prescribed. Do not change the dose without talking to your health care provider. 

If you are taking over-the-counter (OTC) caffeine, follow the instructions that come with the product. OTC caffeine is only meant to be used occasionally. You should not take caffeine instead of sleeping. 

Do not share caffeine that was prescribed for you by a health care provider with other people, even if they have the same condition as you. It may harm them.

Keep caffeine out of the reach of children.

There are multiple forms of caffeine available. Read and follow the instructions for the product you have and make sure you understand how to use it properly. If you have any questions, talk to your health care provider.

Caffeine is found in many foods and drinks. Your body handles caffeine the same way whether you eat it, drink it, or take it as a medicine or supplement. Keep track of all sources of caffeine to make sure you are not getting too much. Too much caffeine can be harmful.

Avoid taking caffeine late in the day. Taking it late in the day may make it harder for you to sleep. 

Stop taking caffeine and talk to your health care provider if you continue to feel tired or have trouble staying alert. Your health care provider may want to check to see what is going on.

If you are using prescription caffeine liquid, look at the liquid before measuring the dose. The liquid should be clear and colorless, without any particles in it. You should not use it if it is cloudy, the color has changed, or you can see things floating in it. 

Use an accurate measuring device to measure each dose of prescription caffeine liquid. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use. Each vial should only be used one time. After measuring the dose, throw away any used medicine. A new vial should be used for the next dose.

If you are using caffeine for breathing pauses in your baby, tell your health care provider right away if the breathing pauses keep happening. Keep all appointments with your health care provider. Also tell your baby’s health care provider right away if your baby has any of the following symptoms.

  • Increased diaper wetting
  • Fast heartbeat
  • Jitteriness, shakiness, or restlessness

What should I tell my health care provider before using caffeine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if caffeine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Other Medicines and Supplements. Caffeine may interact with other medicines and supplements. Before taking caffeine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how caffeine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Also tell your health care provider how much caffeine you usually get from foods and drinks. Your health care provider will let you know if you should take caffeine while you are pregnant or trying to get pregnant.

Breastfeeding. Caffeine passes into breast milk. It can cause fussiness or sleeping problems in breastfed babies, especially if you have large amounts of caffeine. Tell your health care provider if you are breastfeeding or plan to breastfeed. Also tell your health care provider how much caffeine you usually get from foods and drinks. Your health care provider will let you know if you should take caffeine while breastfeeding.

Interactions

Does caffeine interact with foods or drinks?

Caffeine is found in many foods and drinks, including coffee, tea, soda, protein bars, chocolate, and many other products. Your body handles caffeine the same way whether you eat it, drink it, or take it as a medicine or supplement. Keep track of all of your caffeine sources to make sure you are not getting too much. Too much caffeine can be harmful. 

Caffeine and alcohol may have opposite effects. When the two are used together, you may feel like either the caffeine or alcohol is not affecting you like it usually does. This may lead you to drink more alcohol or have more caffeine than you otherwise would and may increase the risk of side effects.

Does caffeine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking caffeine.

  • Fluconazole (Diflucan), itraconazole (Sporanox, Tolsura), ketoconazole, posaconazole (Noxafil), or voriconazole (Vfend), which are medicines used for fungal infections
  • Cimetidine (Tagamet HB), which is a medicine used for heartburn
  • A barbiturate, such as butalbital, phenobarbital, or primidone, which is a medicine that may be used to treat insomnia, migraines, or seizures
  • Phenytoin (Dilantin, Phenytek, and others), which is a medicine to control seizures
  • Theophylline (Elixophyllin, Theo-24), which is a medicine for asthma or certain other breathing problems

Many other medicines may alter the blood levels of caffeine and vice versa. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with caffeine. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much caffeine?

If you or someone else has used too much caffeine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of caffeine?

Alertness. If you are taking caffeine for alertness or to stay awake, it is meant to be taken only when needed. Take it according to the package directions or as your health care provider recommends. Do not take double or extra doses. 

Breathing. If caffeine is prescribed for breathing pauses in a premature baby and a dose is missed, contact your health care provider for instructions.