does mucinex make you tired

Have trouble breathing? Or have a nasty cough making your day difficult? Mucinex can give effective relief in a matter of minutes. But while results are prompt, some say it can make you feel fatigued. But does Mucinex make you tired? We’ll break down the facts below…

Does Mucinex Make You Tired?

Yes, the regular Mucinex product can make you tired, especially if it is paired with other cold & flu medications. Its active ingredient is guaifenesin, which is an expectorant that has “mild to moderate sedative activity.”

*Note: Mucinex Nightshift is specifically designed for use at night and will definitely make you feel tired and sleepy.

What Does Mucinex Do?

mucinex logo

Mucinex is a brand name for guaifenesin and belongs to a class of medicines known as expectorants. It was formally approved by the US FDA in 1952 and is one of the few drugs readily available and used as an expectorant. 

Mucinex indirectly acts on the gastrointestinal vagal nerves, which trigger reflex secretion from submucosal glands and goblet cells — there, it affects mucus secretion from the goblet and Clara cells, resulting in reduced mucin production and secretion and mucus viscoelasticity, which increases the mucus layer’s hydration and loosening congestion in the chest and throat, making it easier for it to be coughed out.

Given its expectorant nature, this agent is often used as a combination component of various prescription and non-prescription over-the-counter cough and cold medications and is a widely available over-the-counter generic medication used to temporarily relieve coughs caused by the common cold, bronchitis, asthma, and other breathing problems. It has also been used as a component of OTC analgesics containing paracetamol.

According to one study, guaifenesin also works as a centrally acting muscle relaxant, preclinically and clinically. At certain doses, it provides symptomatic relief of upper back musculoskeletal pain and spasm. In some cases, guaifenesin is combined with ketamine and xylazine to induce anesthetic in animal food patients. 

Does Mucinex Make You Tired & Sleepy? – Side Effects

Does Mucinex make you sleepy? — Yes, it does. Here’s how it works.

Due to it being a muscle relaxant, guaifenesin also causes mild to moderate sedative properties, which typically induce drowsiness, grogginess, or sleepiness. Not only that, it can negatively affect your cognitive abilities, leaving you confused and unable to concentrate well, making tasks like driving and studying difficult. It can also increase your risk of falls, cause a dry mouth, and problems urinating.

As a result, most people prefer to take muscle relaxers like guaifenesin at night, not only due to the side effects rendering them unable to concentrate on their daily grind or do activities, but also because the medication’s pain relief effect helps them get a more restful, comfortable, and spasm-free night of sleep.

As an expectorant, Mucinex doesn’t cause adverse effects for the most part. But when combined with other medications such as all-in-one cold or flu medicines, it is more likely to cause side effects, which include tiredness (fatigue), sleepiness, or dizziness.

Other Side Effects

Guaifenesin side effects tend to occur occasionally, and most don’t require medical attention. These may go away on their own during treatment as the body adjusts to the medication. The most commonly reported side effects are:

  • Decreased uric acid levels
  • Diarrhea
  • Dizziness
  • Headache
  • Nausea or vomiting (or both)
  • Rashes
  • Stomach pain

Mucinex may occasionally cause nausea, vomiting, and stomach pains when one takes more than the prescribed amount on the packaging. Try taking it with food or a glass of milk to counteract these symptoms.

Rare, but serious side effects include: 

While overdosing on guaifenesin is also unlikely to produce toxic effects given its low toxicity, studies show that kidney stones can form as a result of taking large quantities of guaifenesin. It’s important to never exceed beyond the amount prescribed by your doctor or pharmacist.

On the positive side, guaifenesin has not been known to cause abuse/dependence problems compared to other OTC cough and cold medications and has been proven safe in studies for use in conditions such as URTIs and stable chronic bronchitis.


No known set of drugs have been fully determined to interact with Mucinex, but their absence does not necessarily mean no interactions exist. However, the following drugs have been singled out for possible interactions with Mucinex, though further research is still needed to confirm them:

  • Amitriptyline 
  • Imipramine 
  • Isocarboxazid
  • Phenelzine
  • Phentermine
  • Selegiline

While their effects haven’t been fully determined, each may have varying levels of interactions, which could cause the medications to lose their effects. If you believe you are experiencing an interaction, contact a healthcare provider immediately.

Best Time To Take Mucinex

Take Mucinex by mouth with or without food every 12 hours or as prescribed by your doctor. Do not crush, chew or break the tablet. Swallow whole with a full glass of water. Drinking more fluids while taking Mucinex can help loosen the congestion and lubricate your throat better.

Keep out of reach from children under the age of twelve. Avoid exceeding the maximum recommended dosage of four tablets in 24 hours. If you are using liquid medicine, ensure you measure it with a properly calibrated measure. You can measure it with a dosing syringe, dose-measuring spoon, or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

If you are taking the medication regularly, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up for the missed dose.

Avoid taking a cough suppressant simultaneously with Mucinex because the cough reflex is needed to allow you to cough up loosened phlegm or mucus. See your doctor if your cough worsens, is accompanied by other symptoms such as a fever, rash, or a persistent headache, or lasts for more than seven days.


Mucinex is a powerful expectorant that provides effective relief by loosening mucus in the airways and clearing congestion in the chest and throat to make breathing easier and more comfortable. Though occasionally, it may cause mild side effects like drowsiness and sleepiness due to its muscle relaxant properties, which can hinder your productivity.

Consult your doctor if you have any doubts about taking this drug. Checking with your doctor for side effects is also important if you’re taking other drugs for other existing conditions.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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