The Side Effects of Tylenol

Tylenol (acetaminophen) is an over-the-counter medication used as a pain reliever and a fever reducer. Tylenol may also be used to treat headaches, muscle aches, arthritis, backaches, toothaches and colds. Although Tylenol is a relatively safe drug, using more than 1 gram (1,000 mg) per dose and more than 4 grams (4,000 mg) per day can results in significant liver damage. recommends using no more than 2 grams per day. As with all medications you are taking, you should be aware of the associated side effects and what to do if you experience them.

Gastrointestinal System Side Effects

Overall, side effects of Tylenol are rare. However, symptoms that you experience may be a sign of sensitivity to Tylenol or a sign of overdose. Side effects due to sensitivity include bloody or black stools, or bloody or cloudy urine, states the Mayo Clinic. These effects occur because Tylenol may damage the lining of your gastrointestinal tract. Stop taking Tylenol immediately and talk to your doctor. Signs of an overdose include diarrhea, nausea and vomiting, stomach cramps or swelling or tenderness in the upper abdomen. These signs occur because taking too much Tylenol can damage your liver and cause these symptoms. Seek immediate medical treatment to reduce the effects of overdosing on Tylenol.

Skin Side Effects

Tylenol may cause unwanted side effects to your skin, states the Mayo Clinic. You may notice pinpoint red spots on the skin, skin rash, hives or itching or sores on your lips or in your mouth. Do not apply any skin creams to your rash. Instead, stop taking Tylenol and let your doctor know of the side effects that you are experiencing.

Nervous System Side Effects

The Mayo Clinic states that Tylenol may cause you to feel tired or weak. This occurs because Tylenol alters certain chemical signals that are related to pain in the brain. While Tylenol is effective in altering these signals, it may alter other chemicals in your brain that keep you awake and alert. Therefore, use caution when driving or operating heavy machinery. Your body will likely adjust to the nervous system effects of Tylenol over time.

About this Author

Jacques Courseault, M.D., began writing professionally in 2007. He is currently the fitness editor for, founder and writer of, and co-founder of Don’t Weight to Lose. He is a resident in physical medicine and rehabilitation. Dr. Courseault received his bachelor’s degree in psychology at Tulane University, and is a graduate of Tulane University School of Medicine.