If mucus sits in your airways, bacteria can also sit and grow there. That bacteria can lead to infection. When you need a little help breaking up congestion in your chest, you might consider Mucinex.

The main active ingredient in Mucinex is guaifenesin. It’s quite possible that you can use Mucinex and have no side effects. In fact, most people don’t. Still, this drug can cause some side effects in some people.

The side effects that people can experience with Mucinex are usually mild to moderate. Some of the common side effects typically affect three different systems of the bodies.

The digestive system

Mucinex may cause the following digestive issues:

  • stomach pain
  • nausea
  • vomiting
  • diarrhea

The nervous system

Mucinex may also cause:

  • dizziness
  • headache
  • drowsiness


Mucinex can sometimes lead to rash.

You may find that you get the treatment you need from Mucinex, but the side effects are bothersome. There are some things you can do to help ease these side effects. For example, if Mucinex upsets your stomach, try taking it with food or a glass of milk.

Generally, if you use Mucinex as directed, you shouldn’t have serious side effects. However, overuse or misuse of the drug can cause problems. Using this drug at a dosage that’s too high may increase your risk of kidney stones.

Learn more: Symptoms of kidney stones »

Mucinex is an expectorant. It’s used to treat chest congestion and cough. It helps relieve chest congestion by breaking up mucus that’s stuck in your airways so you can cough it up.

Mucinex comes in tablets or a liquid. Only people who are 12 years and older should take the tablets. They are not approved for use in children younger than 12 years. However, children as young as 4 years can use liquid Mucinex or Mucinex Mini-melts, which are granules that you sprinkle on your child’s tongue. Both of these products are specifically marked for children on the packaging.

If your child is younger than 4 years, talk to your doctor about the best way to treat your child’s cough. Side effects of Mucinex in children are generally the same as they are in adults.

Overall, when you use Mucinex as directed, you probably won’t have side effects. And if you do have any, the side effects are usually mild. If Mucinex upsets your stomach, taking it with food or milk may help. You should only use Mucinex for cough and chest congestion from mucus buildup. If you have other types of coughs or are not sure what is causing your cough, talk to your doctor before using Mucinex. You should also check first with your doctor before using Mucinex if you take other medications or have other medical conditions.