What is an acetaminophen level test?

This test measures the amount of acetaminophen in your blood. Acetaminophen is a medicine used in many over-the-counter (OTC) and prescription medicines. It is used to relieve pain and reduce fever. It comes in liquid, chewable, capsule, or pill form. It is found in many brand name medicines, including Tylenol and Excedrin. Outside the U.S., it's called paracetamol. Acetaminophen can also be combined with other active ingredients in medicines that treat allergy, cough, colds, flu, and sleeplessness.

Acetaminophen is safe when taken at the proper dose. However, taking too much of it can cause an acetaminophen overdose or toxicity. This may cause serious and sometimes deadly liver damage.

Unfortunately, it's common for people to accidentally take too much and have an acetaminophen overdose. It can happen if you:

• Take more than one medicine that contains acetaminophen. For example, you may not realize that a cold, flu, allergy, or other medicine you are taking contains acetaminophen. If you take that medicine plus another medicine that contains acetaminophen, you may end up taking an unsafe dose.
• Aren't following the dose recommendations in the instructions. For example, you might take more than the maximum dose or multiple doses more often than you are supposed to. The adult maximum dose is generally 4000 mgs in 24 hours. But that may be too much for some people. Check with your health care provider to see how much medicine is safe for you. Children's dosing recommendations depend on their weight, age, whether the medicine is in a liquid or solid form, if they are taking additional medicines that also have acetaminophen, and if they are taking any other medicines.
• Give a child an adult version of the medicine, rather than the children's version.

Check with your provider before taking medicines containing acetaminophen for more than ten days, or five days for your child. When you take most medicines, including acetaminophen, your liver breaks them down and filters out the toxins. It may be hard for your liver to keep up if you're taking medicines containing acetaminophen for an extended time.

Other names: acetaminophen drug test, acetaminophen blood test, Paracetamol test, Tylenol drug test

What is it used for?

The test is used to find out if you or your child has taken too much acetaminophen. It may also be used to monitor how well the treatment of an overdose is working.

Why do I need an acetaminophen level test?

Your provider may order this test if you or your child has symptoms of an overdose. When you take too much of the medicine, your liver cannot process the excessive dose and it can build up in your body. Symptoms may happen as soon as two to three hours after taking the medicine but can take as long as 12 hours to appear.

Symptoms in adults and children are similar and may include:

• Nausea and vomiting
• Diarrhea
• Abdominal (belly) pain
• Loss of appetite
• Trouble breathing
• Fatigue
• Irritability
• Sweating
• Jaundice, a condition that causes your skin and eyes to turn yellow

Acetaminophen overdose can be a life-threatening emergency if not treated quickly. If you think you or your child has taken too much acetaminophen, or you notice early symptoms of an acetaminophen overdose, call 911 or go to the nearest emergency room.

What happens during an acetaminophen level test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for an acetaminophen level test.

Are there any risks to an acetaminophen level test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If results show a high level of acetaminophen, you or your child may be at risk for liver damage and may need immediate treatment. The type of treatment will depend on how much excess acetaminophen is in your system. After you get your results, your provider may recommend other tests or treatment. They may repeat this test every four to six hours to make sure you are out of danger.

If you have questions about your results, talk to your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an acetaminophen level test?

Before you or your child take any medicine, read the label carefully. Make sure that you only use the recommended dose. Check the ingredient list to see whether the medicines contain acetaminophen so that you don't take too much. Some common medicines that may contain acetaminophen include:

• Nyquil
• Dayquil
• Dristan
• Contact
• Theraflu
• Actifed
• Mucinex
• Sudafed

Also, if you drink three or more alcoholic beverages a day, ask your provider if it is safe to take acetaminophen. Drinking alcohol while taking acetaminophen can increase your risk of liver damage.

Keep medicines out of reach of children and don't take medicines with acetaminophen for more than ten days without talking to your provider.