Mucinex (Guaifenesin) – Oral

What Is Mucinex?

Mucinex (guaifenesin) is an over-the-counter (OTC) medication used to help relieve chest congestion from a cold or flu. 

Mucinex belongs to a group of drugs called expectorants. Expectorants make it easier for you to cough up phlegm by loosening and thinning the mucus in your lungs.

Mucinex is available in several different nonprescription preparations, including tablets, liquids, and dissolving granules. Several OTC cough and cold combination products also contain guaifenesin as an ingredient.

Drug Facts

Generic Name: Guaifenesin

Brand Name: Mucinex

Drug Availability: Over the counter

Therapeutic Classification: Expectorant

Available Generically: Yes

Controlled Substance: N/A

Administration Route: Oral

Active Ingredient: Guaifenesin

Dosage Form(s): Tablet, extended-release tablet, solution, syrup, liquid, packet

What Is Mucinex Used For?

The Food and Drug Administration (FDA) approved Mucinex to help loosen mucus (phlegm) and thin lung secretions, making it easier for you to cough up mucus and clear your lungs. 

Mucinex is often used to improve symptoms of the common cold and other acute lung infections, but it won't treat your cold or help you recover any faster.

Mucinex (Guaifenesin) Drug Information - Illustration by Zoe Hansen

Verywell / Zoe Hansen

How to Take Mucinex

Mucinex comes in many different formulations, including extended-release (ER) tablets, liquids, and dissolving granules. It’s important to follow the instructions on the package carefully to ensure you’re taking the correct amount.

Guaifenesin is present in many combination cough and cold products. Always review the list of active ingredients of all medicines you are using to ensure guaifenesin is not present in more than one product.

You can take Mucinex with or without food, but taking it with food can help if it causes an upset stomach. Mucinex tablets should be taken with a full glass of water. Staying well-hydrated helps all Mucinex products work. Generally, aim to drink at least eight 8-ounce glasses of water. Try to stick to non-caffeinated drinks.

If you’re using the Mucinex ER tablets, swallow them whole, without crushing, chewing, or breaking them.

If you’re using the dissolving granules, empty the packet onto your tongue and swallow. Try not to chew the granules to avoid an unpleasant taste.


You can store Mucinex at room temperature. Keep Mucinex and all your medications in a safe location, away from children and pets.

Off-Label Uses

Your healthcare provider may prescribe Mucinex to help with chest congestion for conditions not intended to be treated by the product, including lung diseases like chronic bronchitis. If you have a chronic lung condition, only use Mucinex if your provider recommends it.

How Long Does Mucinex Take to Work?

Mucinex should begin to work the first day you start using it. Let your healthcare provider know if your symptoms haven’t improved within seven days or if you have a high fever, rash, or headache that doesn’t go away.

What Are the Side Effects of Mucinex?

This is not a complete list of side effects and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects

Most people don’t experience any side effects while taking Mucinex, but let your healthcare provider know if you develop any reactions, including:

  • Headache
  • Nausea 
  • Vomiting

Severe Side Effects

Rarely, Mucinex may cause severe side effects. Call your healthcare provider right away if you develop any severe symptoms. Call 911 if you think you are having a life-threatening reaction.

Mucinex may cause an allergic reaction that can sometimes be serious. Contact your provider right away if you develop:

  • Hives 
  • Itchy, red, swollen, blistered, or peeling skin 
  • Rash 
  • Swelling of the mouth, face, lips, tongue, or throat 
  • Tightness in the chest or throat
  • Trouble breathing, talking, or swallowing 
  • Unusual hoarseness 
  • Wheezing

Report Side Effects

Mucinex may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Mucinex Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For regular (short-acting) oral dosage forms (capsules, oral solution, syrup, or tablets):
    • For cough:
      • Adults—200 to 400 milligrams (mg) every four hours.
      • Children 6 to 12 years of age—100 to 200 mg every four hours.
      • Children 4 to 6 years of age—50 to 100 mg every four hours.
      • Children and infants up to 4 years of age—Use is not recommended .
  • For long-acting oral dosage forms (extended-release capsules or tablets):
    • For cough:
      • Adults—600 to 1200 mg every twelve hours.
      • Children 6 to 12 years of age—600 mg every twelve hours.
      • Children 4 to 6 years of age—300 mg every twelve hours.
      • Children and infants up to 4 years of age—Use is not recommended .


Cough and cold combination products, including those containing guaifenesin, the active ingredient in Mucinex, can cause severe reactions and death in young children. Do not use these products in children younger than 4 years old.

For children over 4 years, be sure you select a children’s product approved for the child’s age (this information will be on the packaging). Read the instructions carefully to ensure you give the correct dose for the child’s age and weight. Never use an adult product on a child. If you have any questions about choosing a product or how much to give, ask a pediatrician or pharmacist.

Missed Dose

Mucinex is typically taken as needed, meaning only when you have symptoms. If your healthcare provider has told you to take Mucinex regularly, take your missed dose as soon as you remember. If it’s almost time for your next dose, skip the missed dose and resume your normal dosing schedule. Don’t double up or take extra Mucinex.

Overdose: What Happens If I Take Too Much Mucinex?

There is limited information regarding the effects of a Mucinex overdose, though it is not expected to cause severe symptoms. High doses of Mucinex may cause nausea and vomiting. Taking high doses of Mucinex for a long time can also cause kidney stones.

What Happens If I Overdose on Mucinex?

If you think you or someone else may have overdosed on Mucinex, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Mucinex, call 911 immediately.


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If your cough has not improved after 7 days or if you have a fever, skin rash, continuing headache, or sore throat with the cough, check with your doctor. These signs may mean that you have other medical problems.

What Are Reasons I Shouldn’t Take Mucinex?

Do not take Mucinex if you are allergic to guaifenesin or any other ingredient included in the combination products. Always check the list of active ingredients on the packaging to ensure the product does not contain a medication you are allergic to.

Do not use these products in children younger than 4 years old.

What Other Medications Interact With Mucinex?

Mucinex may interact with other medications you take. Always keep an updated list of all your medicines, including OTC products, and share this information with your healthcare provider anytime there are changes.

Certain liquid forms of Mucinex contain alcohol. Avoid using these products with the following medications since unpleasant and sometimes serious reactions may result:

  • Antabuse (disulfiram)
  • Solosec (secnidazole)

This is not a complete list of all the drugs that may interact with Mucinex. Always ask your provider before starting anything new.

Frequently Asked Questions

  • What is Mucinex used for?

    Mucinex is used to improve chest congestion caused by colds and acute lung infections.

  • How does Mucinex work?

    Mucinex is an expectorant and works by thinning lung secretions and loosening mucus (phlegm). This makes it easier for you to cough up mucus and clear your lungs.

  • When should you see your healthcare provider?

    Call your provider if your symptoms don’t improve within seven days or you have a high fever, rash, or headache that does not go away. Don’t take Mucinex for a chronic lung condition (such as asthma or chronic obstructive pulmonary disease, or COPD) unless your provider recommends it.

How Can I Stay Healthy While Taking Mucinex?

If you find yourself searching the shelves at the drugstore looking for something to relieve your cold symptoms, Mucinex may be one product that can help. Just remember, Mucinex won’t treat your cold or help you get better any faster. Getting plenty of rest and staying hydrated is key.

Other remedies, such as using a humidifier or saline nasal irrigation, can also help relieve symptoms of congestion.

If you’re still not feeling yourself after seven days or if you have a high fever, rash, or headache that doesn’t go away, be sure to see your healthcare provider. These could be symptoms of another condition that requires treatment.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. National Library of Medicine. MedlinePlus. Guaifenesin.

  2. UpToDate. Guaifenesin: patient drug information.

  3. Albrecht HH, Dicpinigaitis PV, Guenin EP. Role of guaifenesin in the management of chronic bronchitis and upper respiratory tract infections. Multidiscip Respir Med. 2017;12:31. Published 2017 Dec 11. doi:10.1186/s40248-017-0113-4

By Christina Varvatsis, PharmD
Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.