Medically reviewed by Femi Aremu, PharmD

Tylenol (acetaminophen) is commonly used to temporarily relieve mild pain and headaches, and lower fever. Its therapeutic effect lasts in the body for four to eight hours, depending on the dose and formulation taken.

A drug’s half-life is the time it takes to decrease by half of its starting concentration in the body.

A medication's half-life affects the duration of action and is one factor used in determining a suitable dosing interval. Drugs with a longer half-life take longer to leave the body, so they can be taken less frequently than drugs with a shorter half-life, like Tylenol, which must be taken multiple times daily to sustain its effects.

This article will discuss the different formulations of Tylenol, how long their effects last, and important safety considerations when taking acetaminophen.

How Long Does Tylenol Last?

Tylenol's pain-relieving and fever-reducing effects typically last four to six hours with the regular strength formulation. Extended-release formulations can last for about eight hours.

The half-life of Tylenol is 1.9 to 2.5 hours. Tylenol is metabolized by the liver, so half-life varies slightly from person to person based on the speed at which each person’s liver breaks down the drug.

Another factor that affects how long a drug works in the body (duration of action) is the dose taken.

By taking a higher dose of acetaminophen, you extend its duration of action since the higher starting concentration will take more half-lives to clear from the body.

For example, taking two 650-milligram (mg) tablets results in a much higher concentration than two 325-milligram tablets. Therefore, the 650-milligram tablets last longer in the body and don’t need to be taken as often.

The table below summarizes available preparations of Tylenol.

How Long Is Tylenol Detectable in Breast Milk?

When a lactating person takes Tylenol, peak levels in breast milk occur within one to two hours. However, it is undetectable after approximately 12 hours after ingestion.

Acetaminophen is a good choice for pain and fever relief in nursing individuals due to the small amount of drug transferred into breastmilk and the low incidence of adverse effects in nursing infants. Furthermore, acetaminophen is a drug used to treat infant fevers or pain.

How Long Does Tylenol Take to Work?

Tylenol tablets may start to work within 45 minutes of taking it for pain relief. However, the effervescent or dissolvable tablets may work more quickly—within 20 minutes. Still, the specific timing to when you will feel relief can vary from person to person.

How to Take Tylenol Safely

Tylenol is a safe medication when taken as directed. For extra-strength Tylenol (500 milligrams) and 650-milligram tablet formulations, wait six to eight hours between doses. Do not take more than six tablets in 24 hours unless directed by a healthcare provider.

For regular-strength Tylenol and acetaminophen 325-milligram tablets, wait four to six hours between doses. Do not take more than 10 tablets in 24 hours. For children under 12 years of age, consult a healthcare provider for dosing by weight.

Tylenol Overdose and Toxicity

Severe liver damage can occur from taking too much acetaminophen in a short time period.

The maximum dose of acetaminophen for adults is 4,000 milligrams in 24 hours for people with a healthy liver and five doses (1,625 milligrams) in 24 hours for children.

You may also be at risk of liver damage if you take Tylenol and:

• Are taking other drugs containing acetaminophen at the same time

• Drink three or more alcoholic beverages every day

• Have existing liver problems

In these cases, your maximum daily dose of Tylenol may be lower.

Many over-the-counter (OTC) and prescription medications contain acetaminophen (e.g., Dayquil, Nyquil, Excedrin, Percocet). The daily maximum dose counts all acetaminophen from all sources.

It is important to read medication labels to know the active ingredients in OTC and prescription medications you take. Note that acetaminophen is referred to as paracetamol in countries outside of the US and is the same medication.

Summary

Tylenol (acetaminophen) is an OTC medication commonly used to treat minor pain, headaches, and fevers. There are several different formulations that vary in strength and dosing.

Tylenol’s therapeutic effect typically lasts four to six hours, though taking an extended-release formulation or a larger dose can prolong the effects to about eight hours.

Be sure to read medicine labels to identify all OTC products that contain acetaminophen. The total daily dose of acetaminophen should not exceed 4,000 milligrams from all sources, as this can lead to liver damage.

Frequently Asked Questions

How long does Tylenol last for a fever?

The fever-reducing effects of Tylenol last about four to six hours, so it needs to be taken multiple times a day to treat an ongoing fever. Consult a healthcare provider if the fever lasts more than three days or worsens.

Is it OK to take Tylenol every day?

Tylenol is intended for short-term use. Consult a healthcare provider if you need Tylenol for more than 10 days. Taking a pain reliever like Tylenol daily can sometimes worsen headaches or cause medication overuse headaches.