Does Mucinex show up on a drug test? 

Does Mucinex show up on a drug test? 

No, Mucinex (Guaifenesin) does not show up on a drug test. Mucinex is one of the most commonly used OTC medications which is an expectorant and helps loosen up thick mucus that blocks up your airways. Mucinex is not a controlled substance. 

In fact, Guaifenesin – the active ingredient in Mucinex, is one of the safest medications that can be used concomitantly with almost every other medication and it does have a minimal side effect profile (1). 

It is far from being a controlled substance or a drug of abuse. So no, Mucinex does not show up on a drug test. However, there are a number of different Mucinex formulations which contain other active ingredients – apart from Guaifenesin. 

One example is Mucinex DM, which contains Guaifenesin and Dextromethorphan. Although Dextromethorphan is not a controlled substance and it is not structurally similar to them either, it can cause a false positive for Phencyclidine (PCP) (2)

This is why you need to make sure which Mucinex formulation you’re currently using. If it’s the original Mucinex that only contains Guaifenesin, there’s nothing to worry about. 

How long does Dextromethorphan in Mucinex DM stay in your body? 

Dextromethorphan has a half-life of about 4 hours, which is the time taken by this drug to reduce its initial concentration to half. 

The remaining concentration keeps reducing to half after every 4 hours until the entire medication is eliminated from your body. This process can take a day or two. 

How to avoid a false positive caused by Mucinex DM? 

You can avoid getting a false positive on Mucinex DM by making sure that you don’t take this medication 24-48 hours before your test. This is an OTC medication and there’s no harm in skipping it for a day or two. 

This way your body will have enough time to eliminate your last Mucinex DM dose. If you have a drug test coming up, you can take this precaution to avoid getting a false positive. 

Was this helpful?

Thanks for your feedback!



U.S. National Library of Medicine. Drug Information: Guaifenesin [Internet]. MedlinePlus; [cited 2023 Jan 10]. Available from:


Alyson Schwebach, Jennifer Ball. Urine Drug Screening: Minimizing False Positives and False Negatives to Optimize Patient Care. US Pharm. 2013;38(12):1-6. Available at: