How long does Tylenol last?

Tylenol (active ingredient acetaminophen) is a popular over-the-counter (OTC) medication used as a pain reliever and fever reducer. You might reach for the medicine cabinet staple when you have a headache, arthritis pain, or fever. It’s readily available in many forms, such as tablets, capsules, and liquid suspensions. When taken in appropriate doses and short durations, Tylenol is generally considered safe for most people, including children, pregnant and breastfeeding women, and older adults.

Because of its safety and effectiveness, Tylenol is considered a first-line treatment for mild-to-moderate pain and fever. In general, Tylenol lasts from four to six hours. That said, the duration of action for acetaminophen can vary based on dosage, metabolism, and other factors.

Keep reading to find out how long acetaminophen lasts, the dosing intervals for different Tylenol products, and what to know about Tylenol toxicity.

How long does acetaminophen last?

The standard formulation of Tylenol typically lasts four to six hours. In comparison, extended-release formulations may last eight hours or more, says Ila Dayananda, MD, a board-certified OB-GYN and Chief Medical Officer of Oula Health. For the standard formulation, “Acetaminophen has a relatively short half-life, being about 2-3 hours in adults, meaning it is metabolized and eliminated from the body relatively quickly,” says Dr. Dayananda.

Dr. Dayananda says acetaminophen is metabolized (broken down) mainly in the liver to inactive metabolites before being excreted in the urine. That said, a small percentage is metabolized by a group of liver enzymes, forming a toxic metabolite called N-acetyl-p-benzoquinone imine (NABQI).

“Under normal circumstances, this toxic metabolite is quickly neutralized by glutathione (an antioxidant) in the liver; however, in cases of overdose, glutathione stores can become depleted, leading to liver damage and potentially liver failure,” explains Dr. Dayananda.

She says factors that may affect the duration of action of acetaminophen include the dosage, formulation, personal metabolism, liver function, and whether or not other medications or substances that can interact with acetaminophen are present.

How long is Tylenol detectable in breast milk?

According to research, Tylenol reaches its peak concentration in breast milk within one to two hours of ingestion and becomes undetectable by 12 hours.

“Acetaminophen is generally considered safe and recommended for use while breastfeeding and during pregnancy when used as directed,” says Dr. Dayananda. It is one of the preferred pain relievers for pregnant and breastfeeding individuals because it has been extensively studied and has a low risk of adverse effects when taken in recommended doses.

How long does Tylenol take to work?

“Tylenol typically takes about 30 minutes to one hour to start working after taking it, where the onset of action will vary depending on dosage form (e.g., regular versus Extra Strength Tylenol) and personal metabolism,” says Dr. Dayananda. For example, IV acetaminophen starts working in 5 to 10 minutes, immediate-release acetaminophen takes 10 to 60 minutes, and the effervescent and liquid forms can take 20 minutes to kick in. Taking your dose of Tylenol on an empty stomach can also make it work faster.

RELATED: How long does it take for Tylenol to work?

Tylenol overdose and toxicity

When taken according to the label’s instructions, Tylenol is very safe, according to the National Poison Control Center. Even so, Tylenol overdose is one of the most common poisonings. In fact, research indicates that Tylenol overdose causes 56,000 visits to the emergency department, 2,600 hospitalizations, and 500 deaths in the United States yearly. In 50% of cases, Tylenol overdoses are unintentional, occurring for the following reasons:

• Individuals may take multiple medications containing acetaminophen, not knowing they contain the same ingredient. For example, many cold, flu, allergy medicines, and OTC sleep aids contain acetaminophen.
• Patients may take the maximum recommended amount of acetaminophen for several days or longer, causing a toxic buildup in their system.
• Individuals who regularly drink alcohol, especially more than three drinks at a time, are at higher risk of an acetaminophen overdose, says Robert Glatter, MD, assistant professor of emergency medicine at Lenox Hill Hospital in New York. That’s because chronic drinkers are more likely to have impaired liver function from chronic liver conditions like cirrhosis (scarring of the liver) or fatty liver disease, adds Medhat Mikhael, MD, pain medicine specialist and medical director of the Spine Health Center at MemorialCare Orange Coast Medical Center Fountain Valley, California. They’re also more likely to experience liver damage due to preexisting liver dysfunction, he points out.
• Children may be at risk if caretakers use an adult formulation or do not carefully measure pediatric preparations.

The U.S. Food and Drug Administration (FDA) issued a Boxed Warning (or black box warning) for acetaminophen—the highest safety warning a medication can have—due to the potential risk of severe liver injury. It emphasizes that individuals should not exceed the maximum daily dose of Tylenol, take it with other OTC or prescription medications containing acetaminophen, or consume alcohol while using Tylenol. The FDA also advises seeking immediate medical attention for the following symptoms:

• Abdominal pain
• Jaundice (yellowing of the skin or eyes)
• Dark urine

Acetaminophen upper daily limits

Dr. Mikhael points out that in cases of acute overdose, people may take too much at once without realizing the potential harmful effects of Tylenol. While the upper limit is 3,250 mg of acetaminophen per day, he says the absolute maximum an adult should take is 4,000 mg, and only if directed to do so by a healthcare provider.

Dr. Mikhael stresses the importance of spreading the doses out, taking no more than a maximum of 1,000 mg, four times daily (every six hours)—the amount in two extra-strength tablets. In adults, acute overdose and liver damage may occur in doses greater than 7,500 mg to 10,000 mg (about 24 regular-strength tablets) are taken within eight hours or less. In children, single doses of 120 mg/kg have been associated with toxicity, but generally, doses exceeding 200 mg/kg are more likely to result in toxicity.

Because toxicity can develop even if you take recommended amounts of Tylenol for an extended period, don’t take it longer than seven to 10 days without consulting a healthcare professional for medical help, Dr. Mikhael advises.“Do not exceed more than 4 g [4,000 mg] a day, and do not take it daily for long periods of time,” he advises. Otherwise, liver damage and other serious effects can occur. Alternating acetaminophen with nonsteroidal anti-inflammatory drugs (NSAIDs) like Aleve (naproxen), Advil, or Motrin (ibuprofen) for pain relief can help reduce the risk of dangerous side effects.

Stages of acetaminophen toxicity

In cases of acetaminophen overdose, the first organ affected is the liver, says Dr. Mikhael. As toxicity becomes more advanced, patients will experience multisystem failure. “The kidneys shut down, the pancreas is inflamed, and it can become life-threatening,” Dr. Mikhael explains.

The good news? Less than 1% of acetaminophen poisoning cases that end up in the emergency room cause death. “From my clinical experience, most people do recover because they feel very sick and seek medical attention early on,” says Dr. Mikhael.

To avoid acetaminophen overdose, it’s important to spot the signs. There are four stages of acetaminophen toxicity, including:

• Stage 1: About 30 minutes to 24 hours after taking acetaminophen, patients are usually asymptomatic but may experience nausea, vomiting, loss of appetite, or general malaise. The severity of symptoms in this preclinical stage will be in direct correlation to the amount of acetaminophen ingested.
• Stage 2:  In the second stage—about 18 to 72 hours after ingestion, Stage 1 symptoms may continue. Dr. Glatter says patients may also have upper right quadrant pain, hypotension (low blood pressure), and tachycardia (fast heart rate). In addition, laboratory values may begin to demonstrate evidence of hepatotoxicity. Many patients do not progress beyond this stage, especially if receiving medical care.
• Stage 3:  If toxicity has not been addressed 72 to 96 hours after taking acetaminophen, patients may progress to this hepatotoxic phase, where severe liver dysfunction may cause jaundice (yellowing of the skin or whites of the eyes), excess bleeding or blood clotting, hypoglycemia (low blood sugar), pancreatitis (inflammation of the pancreas) and central nervous symptoms like confusion due to a buildup of toxins in the blood. Liver failure, seizures, coma, and death may occur in critically ill patients who are not treated, says Dr. Glatter.
• Stage 4: During this recovery phase, the majority of patients who receive treatment will fully recover from symptoms and organ failure within four days to three weeks.

When caught in its early stages, acetaminophen can be treated with oral or intravenous acetylcysteine, brand names Acetadote and Mucomyst. When given within eight hours post-ingestion, it is nearly 100% effective but may be used up to 48 hours after ingestion. Other treatments include activated charcoal (given within the first one to two hours of ingestion) and supportive care such as anti-nausea medication and IV fluids (as needed).

The bottom line: Tylenol lasts four to six hours

Regular-strength Tylenol starts working 30 minutes to an hour after ingestion, typically lasting for four to six hours. Factors like liver function, metabolism, dosage, and formulation can affect how long Tylenol works. Because severe liver damage and other life-threatening effects can occur from Tylenol toxicity, it’s important to stick to the dosage guidelines and consult a healthcare professional for medical advice if you are taking Tylenol longer than seven days.