Acetaminophen can have side effects. Although they don’t occur in most people, some effects can be serious. This is especially true if you take more than the recommended amount.

Have you ever taken Tylenol to treat mild pain or reduce a fever? If so, then you’ve taken acetaminophen. It’s the generic name for the drug Tylenol. This drug is also sold under many other brand names and is an ingredient in many over-the-counter drugs. It’s quite possible that you’ve taken it and not even known.

Read on to learn about this drug as well as its side effects, including tips on what to do if you experience side effects and how to avoid them altogether.

You can use acetaminophen to relieve mild or moderate pain. This is usually pain from colds, sore throats, headaches, body or muscle aches, menstrual cramps, arthritis, or toothaches. You can also use it to reduce fever.

It’s not fully known how acetaminophen works. It doesn’t reduce swelling or inflammation. Instead, it’s thought that it blocks the release of certain chemicals in your brain that signal the sensation of pain.

Acetaminophen has side effects, but most people don’t experience them. Most people tolerate this drug well. In rare cases, people have had allergic reactions to it. The most concerning side effect, though, is severe liver damage. It usually only happens when you overuse acetaminophen.

Allergic reaction

In very rare cases, some people have had allergic reactions to acetaminophen. Call your doctor immediately if you develop the following reactions after taking acetaminophen:

  • difficulty breathing or swallowing
  • swelling of your face, lips, throat, or tongue
  • hives
  • severe itching
  • peeling or blistering skin

Severe liver damage

Acetaminophen poisoning can happen from taking too much acetaminophen. Your liver processes acetaminophen and converts it into a different substance. If you take large amounts of acetaminophen, your liver produces more of that substance. And when there is too much of it, that substance can damage your liver. However, if you take acetaminophen at the recommended dosage, liver damage from the drug is not likely.

Symptoms of liver damage include:

  • yellowing of your skin or the whites of your eyes (jaundice)
  • pain in the upper right area of your abdomen
  • nausea or vomiting
  • loss of appetite
  • fatigue
  • sweating more than usual
  • pale skin
  • unusual bruising or bleeding
  • dark or tea-colored urine
  • dark, tarry stools

If you suspect you’ve taken too much acetaminophen or notice any of these symptoms, contact your poison control center or get medical help right away. If you know you’ve taken more than the recommended dosage of acetaminophen, go to the nearest emergency room, even if you don’t have any symptoms of liver damage. If someone you know who has taken acetaminophen becomes unresponsive or stops breathing, call 9-1-1 or the number for your local emergency services.

Read more: Acetaminophen overdose causes, treatment, and prevention »

Acetaminophen overuse is more common than you think. That’s because acetaminophen is a common ingredient in many different over-the-counter drugs. Keep track of how much acetaminophen you take in one day. This can decrease your risk of overuse.

Your individual acetaminophen limit may also be affected by your age or certain lifestyle habits. Severe liver damage is more likely to occur in:

  • Adults who take more than 3 g (3,000 mg) of acetaminophen in a 24-hour period
  • Children who take more than five doses in a 24-hour period
  • People who already have liver disease, take other medications that can damage the liver, or drink three or more alcoholic drinks per day, even when they take acetaminophen at the recommended dosage

Before giving acetaminophen to your child, check the package label for instructions. Verify the dosage. The dosage for children is usually in a chart that is based on age and weight. Your doctor or pharmacist can help you with the dosage if the package is unclear to you. If your child is younger than 2 years, talk to their doctor before giving them acetaminophen. And never give your child acetaminophen that is clearly marked for use only in adults.

When used at correct dosages, acetaminophen is a safe and effective drug. It usually has no side effects. However, if you use too much, the side effects can be severe and even deadly. You need to know if any other drugs you take contain acetaminophen so that you don’t go over your daily limit. If acetaminophen is a part of your drug regimen, talk to your doctor to see what that limit is for you.