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Tylenol Side Effects

Side effects of Tylenol (acetaminophen) include nausea, stomach pain, headache, hoarseness, loss of appetite, itching, rash, dark urine, clay-colored stools and swelling of the face, throat, tongue or limbs. Seek medical attention if you experience serious Tylenol side effects.

Last Modified: September 5, 2023
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Common Tylenol Side Effects

Most people taking Tylenol at recommended doses don’t experience side effects. The most common mild side effect of Tylenol is nausea, which occurs in about 34% of patients. Tylenol is also known as acetaminophen and paracetamol.

Common side effects of Tylenol (acetaminophen) include:
  • Constipation
  • Diarrhea
  • Dizziness
  • Headache
  • Itchiness
  • Nausea
  • Sweating
  • Tiredness
  • Vomiting

The frequency of vomiting is second to nausea and impacts 15% of reported cases. Constipation and itching was reported in 5% of cases. Other symptoms happen between 1% to 10% of the time.

Liver Damage From Tylenol

Graphic showing how Tylenol overdose leads to liver damage and/or failure.

The liver breaks down most acetaminophen or paracetamol in a standard dose. It is then eliminated in the urine. However, some of the drug is converted into a by-product that can be toxic to the liver. The likelihood of liver damage varies and sex, age and overall health status can impact this risk.

According to numerous studies, taking 4,000 mg of Tylenol daily for a week can affect your liver. You may even experience severe liver damage if you take more than 4,000 mg of acetaminophen in 24 hours. In addition, you shouldn’t take Tylenol with other drugs that contain acetaminophen or with three or more alcoholic drinks daily.

Overdose Signs and Acute Liver Failure

An overdose’s initial signs and symptoms include diarrhea, sweating and a loss of appetite. Vomiting, stomach cramps and pain in the upper right abdomen are common. Elderly patients who overdose on Tylenol may experience flapping hand tremors related to serious liver damage.

A Tylenol overdose has four distinct phases:
  • Phase 1: Occurs in the first 24 hours after ingesting too much acetaminophen. People usually experience nausea, tiredness (fatigue), anorexia, vomiting, paleness (pallor) and excessive sweating (diaphoresis).
  • Phase II: Occurs about 24 to 72 hours after ingestion. Symptoms may include right upper quadrant abdominal pain, nausea and vomiting. People may also experience a fast heartbeat and low blood pressure.
  • Phase III: Begins about 72 to 96 hours after ingesting Tylenol. Symptoms of liver failure or liver damage include jaundice (yellowing of the skin or eyes), hypoglycemia (low blood sugar), bleeding (coagulopathy) and loss of brain function from toxins. Multiple organ failure and death may also occur at this stage.
  • Phase IV: Applies to those who survive Phase III. This time in recovery lasts from four days up to three weeks, during which the symptoms resolve.

More than 100 products contain acetaminophen. Individuals should be aware that other medications they take (like cold medicine) also have acetaminophen.

How Acetaminophen Causes Liver Failure

Tylenol breakdown leaves traces of a toxic byproduct known as NAPQI. This byproduct can build up and damage the cells of the liver. It is critical to seek treatment immediately if you suspect a Tylenol overdose.

Most doctors pump the patient’s stomach (gastric lavage) to remove any remaining pill fragments. Doctors may give an antidote called N-acetylcysteine, or NAC, that blocks acetaminophen absorption in the body. A liver transplant may be the only way to prevent death if the patient reaches the last stages of liver failure.

Was your child diagnosed with ADHD or ASD after taking Tylenol during pregnancy?

Tylenol and Autism Risk

Some research suggests that taking Tylenol during pregnancy may increase the risk of children developing autism or attention-deficit/hyperactivity disorder, known as ADHD.

More research is necessary because the results are mixed. Scientists do not understand if a causal relationship exists or how it may occur.

A 2022 meta-analysis of 16 quality studies found an association between Tylenol and adverse neurodevelopmental outcomes.

“Acetaminophen is still the safest known drug to take during pregnancy for problems like fever and pain”, said Cleveland Clinic OB/GYN Dr. Salena Zanotti. “When you’re pregnant, it’s riskier to have an untreated fever than it is to take acetaminophen.”

Is There a Link Between Tylenol and ADHD?

Emerging evidence has linked long-term or high-dose use of paracetamol during pregnancy to neurodevelopmental disorders in children, including attention-deficit/hyperactivity disorder (ADHD).

Epidemiological studies increasingly point to a higher relative risk for these disorders after exposure in the womb to paracetamol. Specifically, an analysis of 14 epidemiological studies shows a relationship between prenatal exposure and developmental delays. These include ADHD and a subtype of autism spectrum disorder associated with hyperkinetic behavior.

A 2022 meta-analysis reported that;All 16 studies selected in our data showed a consistent association between acetaminophen and adverse neurodevelopmental outcomes. The effects were particularly stronger for attention/hyperactivity symptoms.

However, many experts feel there’s not enough evidence to establish a firm connection between Tylenol in pregnant women and neurological disorders in their children.

Rare Allergic Skin Reactions

According to the U.S. Food and Drug Administration, rare but severe skin reactions can be associated with acetaminophen. A reaction may occur with first-time use or another time when taking Tylenol (acetaminophen).

Potential skin reactions with acetaminophen include:
  • Acute generalized exanthematous pustulosis (AGEP)
  • Stevens-Johnson Syndrome (SJS)
  • Toxic epidermal necrolysis (TEN)

Signs and symptoms of SJS and TENS include flu-like symptoms, mucous membrane effects and a painful rash that blisters. In addition, the skin may lift and detach from the body. SJS and TEN can even lead to blindness or death.

AGEP is less severe. It causes small bumps that erupt on the trunk, body folds and face. AGEP often resolves within two weeks after the patient stops taking Tylenol.

Can Tylenol Cause High Blood Pressure?

Recent studies looked at the effect of acetaminophen on blood pressure in people with hypertension. In one trial, 4 g of acetaminophen per day for two weeks increased systolic BP 4.7 mm Hg after two weeks in patients with hypertension.

As a result, experts use caution when recommending acetaminophen, especially for patients with hypertension, increased cardiovascular risk and those who may be pregnant. If you are pregnant or have cardiovascular risks or hypertension, discuss whether to use Tylenol with your doctor.

Please seek the advice of a medical professional before making health care decisions.