Can Doxycycline cause a positive drug test? 

Can Doxycycline cause a positive drug test? 

Doxycycline may or may not cause a false positive drug test. Doxycycline is a prescription antibiotic which is used for the treatment of a number of bacterial infections. 

Although it is not a controlled substance per se and doesn’t structurally resemble any drug of abuse either, it can still cause a false positive for Opiates (1). 

This is because of the cross-reactivity of antibodies used in standard urine drug immunoassay and this is exactly why this method of drug testing is considered preliminary. 

In case of a positive result, confirmatory tests may confirm the preliminary findings, which in most cases are not accurate. 

How long does Doxycycline stay in your system? 

Doxycycline has a half-life of about 15-22 hours, which is the time taken by this medication to reduce its initial peak concentration to half. The remaining concentration keeps reducing to half every 15-22 hours until the drug is completely washed out from your body. 

The process can take a few days, typically 4-5. However, this time period is average for healthy adults. People with underlying health conditions, especially hepatic insufficiency, can experience delayed drug metabolism. 

How to avoid Doxycycline showing up on a drug test? 

There is no way to avoid Doxycycline showing up in your drug test if you’re currently taking it. The medication sometimes does not even get detected. However, a false positive on Doxycycline is always considered a possibility. 

In such a case, it’s best to talk to your healthcare provider and keep your prescription with you to submit to the test conducting authorities prior to your drug test. 

This would help them know that you are currently taking a medication that is capable of causing a false positive. These inaccurate findings are pretty common with urine drug Immunoassays. 

More accurate testing procedures like Gas Chromatography – Mass spectroscopy are not associated with false positives (2). However, they are quite expensive and not everyone can afford them. 

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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:


Ramoo B, Funke M, Frazee C, Garg U. Comprehensive Urine Drug Screen by Gas Chromatography/Mass Spectrometry (GC/MS). Methods Mol Biol. 2016;1383:125-31. doi: 10.1007/978-1-4939-3252-8_15. PMID: 26660182. Available from: