Mucinex can cause mild to moderate side effects in some people. This can include digestive symptoms, dizziness, and drowsiness.

If mucus sits in your airways, bacteria can collect and grow there as well. That bacteria can lead to infection.

If you need help breaking up the mucus in your chest, you might consider a type of medication known as an expectorant.

Expectorants are used to treat chest congestion and cough. They help relieve chest congestion by breaking up mucus that’s stuck in your airways so you can cough it up.

The drug guaifenesin is currently the only expectorant that the Food and Drug Administration (FDA) has approved for over-the-counter (OTC) use. It’s found in many popular products, including Mucinex.

Guaifenesin is safe and well-tolerated. It’s quite possible that you can take it or Mucinex and have no side effects. In fact, most people do not. Still, they can cause side effects in some people.

There are multiple versions of Mucinex.

The products that contain guaifenesin are available as a liquid, a tablet, or granules. Products with DM in their names also include small amounts of the ingredient dextromethorphan, which helps suppress cough.

Mucinex products with guaifenesin as their main active ingredient are:

  • Children’s Cough Mini-Melts – Orange Creme Flavor
  • Children’s FreeFrom Cough & Mucus
  • Children’s Multi-Symptom Cold – Very Berry Flavor
  • DM Extended-Release Bi-Layer Tablets
  • Extended-Release Bi-Layer Tablets
  • Maximum Strength DM Extended-Release Bi-Layer Tablets
  • Maximum Strength Extended-Release Bi-Layer Tablets
  • Maximum Strength Fast-Max Chest Congestion Honey & Berry Flavor
  • Maximum Strength Fast-Max DM MAX
  • Maximum Strength Fast-Max DM MAX Honey & Berry Flavor
  • Maximum Strength Fast-Max Severe Congestion & Cough

Most other versions of Mucinex also contain guaifenesin but have acetaminophen as their main active ingredient.

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 body.

The digestive system

Mucinex may cause the following digestive issues:

The nervous system

Mucinex may also cause:

The integumentary system (skin)

Mucinex can sometimes lead to a rash or hives.

Generally, if you use guaifenesin or Mucinex as directed, you should not have serious side effects. However, overuse or misuse can cause problems.

Taking a dosage that’s too high may increase your risk of:

Only people who are at least 12 years old should take Mucinex tablets. The FDA has not approved them for use in children younger than that.

However, children as young as 4 years old can use liquid Mucinex or Mucinex Mini-Melts. Mini-Melts are granules that you sprinkle on the tongue. These products are specifically marked for children on the packaging.

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

Overall, if you use Mucinex as directed, you probably will not have side effects. If you do have any, they’re usually mild.

There are some things you can do to help ease any bothersome side effects. For example, if Mucinex upsets your stomach, try taking it with food or a glass of milk.

Only use Mucinex for cough and chest congestion from mucus buildup. If you have another type of cough or are unsure what’s causing your cough, speak with a doctor before using Mucinex.

Also, check with a doctor before using Mucinex if you take other medications or have other medical conditions. They can help you avoid potentially harmful drug interactions.