Skip to Content

Guaifenesin: 7 things you should know

Medically reviewed by C. Fookes, BPharm Last updated on Aug 30, 2019.

1. How it works

Guaifenesin is an expectorant that increases the volume and reduces the viscosity (stickiness) of respiratory tract secretions. This makes coughing out these secretions easier.

2. Upsides

  • Guaifenesin is used as an expectorant (a substance that promotes mucus secretion in the airways).
  • Usually used in combination with other ingredients.
  • Use to relieve chest congestion that occurs as a result of a cold, the flu, or allergies.
  • Makes a cough more productive. Guaifenesin will not stop coughing; however, coughing is important as it is the body's way to remove excess mucus.
  • Guaifenesin is generally well tolerated.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Nausea and vomiting are the most commonly reported side effects; constipation, dizziness, headache, and a rash are reported rarely. Side effects are generally mild at low dosages.
  • Do not use in children younger than 4.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

4. Bottom Line

Guaifenesin is an expectorant that helps thin and remove mucus from the airways. It is generally well tolerated.

5. Tips

  • Guaifenesin does not need to be taken with food; however, it can be taken with food if it upsets your stomach.
  • Take exactly as directed by your doctor or on the label. Do not increase the dosage or take for longer than is recommended. Use a properly calibrated measuring spoon to measure liquid guaifenesin dosages.
  • Do not open, crush, break, or chew guaifenesin delayed-release capsules or tablets because this may cause too much of the drug to be released at once.
  • Drink extra fluids while you are taking guaifenesin to help loosen congestion and lubricate the throat.
  • Do not drive, operate machinery or perform other hazardous tasks until you know how guaifenesin affects you.
  • Protect guaifenesin liquid from light.

6. Response and Effectiveness

Some effects of guaifenesin should be noticed within 30 minutes of taking it orally; however, up to two days of regular dosing may be needed before the full effects are seen. Liquid guaifenesin lasts for approximately four to six hours. Delayed-release capsules or tablets last for up to 12 hours.

7. Interactions

Guaifenesin has no known drug interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use guaifenesin only for the indication prescribed.

Copyright 1996-2019 Revision date: August 30, 2019.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.