Will medications or dietary supplements affect test results?
There are two common ways that medications and supplements can affect test results: 1) by test interference, or 2) by pharmacological or biological effects.
What is test interference?
Test interference occurs when a medication or dietary supplement alters the test specimen (urine, saliva, stool, blood), or directly interferes with the test reagents used in processing the specimen. Test interference causes an inaccurate result.
What is a pharmacological or biological effect?
Pharmacologic or biological effects of drugs or dietary supplements can change the results of lab tests. Examples of this include: levothyroxine increasing thyroid hormone levels, lisinopril increasing potassium levels, vitamin D3 increasing vitamin D3 and 25-OHD levels, and lactobacillus species probiotics increasing lactobacillus species absolute and relative abundance. Pharmacological or biological effects do not interfere with the lab test; that is, the result is accurate.
Will Vibrant Wellness tell me which medications and supplements interfere with a test and whether to continue or discontinue before testing?
Vibrant Wellness is not a direct-to-consumer lab and does not provide direct patient care. Vibrant cannot provide medical advice on continuing or discontinuing medications or dietary supplements. The ordering provider is the best person to determine personalized pre-test conditions for their patients, as the plan will be informed by the patient's medical history, current symptoms, medications/supplements, allergies/sensitivities, and other diagnostic tests. It is the responsibility of the ordering and treating provider to advise patients on whether to test in medicated, non-medicated, supplemented, or non-supplemented conditions. Vibrant Wellness test specimen collection instructions indicate whether there are fasting restrictions, diet restrictions, medication restrictions, supplement restrictions, or time restrictions based on the test performance accuracy, precision, reliability, and reproducibility in internal validation studies.
How do I know if a specific medication or dietary supplement affects my test results?
Practitioners and patients can read drug labels and dietary supplement labels for information on test interference. If the medication or dietary supplement label does not list information on test interference, contact the manufacturer for more information. Another option is to ask a pharmacist as pharmacies may have access to drug-laboratory test interactions (DLTI) alert databases. However, DLTI databases have several limitations, such as lacking information on clinical relevance of the specific DLTI, scientific literature is listed but not synthesized, cited literature is not up-to-date, literature reports contradictory findings, or information is missing on the degree, duration, and incidence of the interference or specific risk factors of the interaction (such as age or gender) 2,3,4.
Where can I find more information on test interference and elimination half-lives of medications and dietary supplements?
The National Library of Medicine’s Daily Med database5 is a searchable free database which provides the most recent drug and supplement labeling information submitted to the FDA. Drugs.com is another free searchable database6 with information on prescription and over-the-counter medications and supplements. A Google or Google Scholar search will also provide information on half-lives of medications and dietary supplement ingredients (e.g., capsaicin, turmeric, omega-3 fatty acids).
If I want to discontinue a medication or dietary supplement to establish a baseline finding, how long does it take medications or dietary supplements to ‘clear’?
With certain medications, the drug itself may have cleared the body, but the effect of the medication may be longer lasting. It is important to realize that there is a great deal of variability in the circulating levels and metabolic clearance rates of medications and dietary supplements. In addition, clearance rates are affected by episodic fluctuations, diurnal rhythm, genetics, age, biological sex, menstrual cycle phase, renal function, liver function, immune function, and comorbidities. A general rule of thumb is to take the half life of the medication or supplement and multiply it x 5 to allow "clearance" of the medication or supplement.
References
- Yao, H., Rayburn, E. R., Shi, Q., Gao, L., Hu, W., & Li, H. (2017). FDA-approved drugs that interfere with laboratory tests: A systematic search of US drug labels. Critical Reviews in Clinical Laboratory Sciences, 54(1), 1–17. https://doi.org/10.1080/10408363.2016.1191425
- van Balveren, J. A., Verboeket-van de Venne, W. P. H. G., Doggen, C. J. M., Cornelissen, A. S., Erdem-Eraslan, L., de Graaf, A. J., Krabbe, J. G., Musson, R. E. A., Oosterhuis, W. P., de Rijke, Y. B., van der Sijs, H., Tintu, A. N., Verheul, R. J., Hoedemakers, R. M. J., Kusters, R., Dutch Society for Clinical Chemistry and Laboratory Medicine, & task group ‘SMILE’: Signaling Medication Interactions and Laboratory test Expert system (2021). Clinical usefulness of drug-laboratory test interaction alerts: a multicentre survey. Clinical Chemistry and Laboratory Medicine, 59(7), 1239–1245. https://doi.org/10.1515/cclm-2020-1770
- van Balveren, J. A., Verboeket-van de Venne, W. P. H. G., Erdem-Eraslan, L., de Graaf, A. J., Loot, A. E., Musson, R. E. A., Oosterhuis, W. P., Schuijt, M. P., van der Sijs, H., Verheul, R. J., de Wolf, H. K., Kusters, R., Hoedemakers, R. M. J., & Dutch Society for Clinical Chemistry and Laboratory Medicine, task group ‘SMILE’: Signaling Medication Interactions and Laboratory test Expert system (2018). Impact of interactions between drugs and laboratory test results on diagnostic test interpretation - A systematic review. Clinical Chemistry and Laboratory Medicine, 56(12), 2004–2009. https://doi.org/10.1515/cclm-2018-0900
- van Balveren, J. A., Verboeket-van de Venne, W. P. H. G., Erdem-Eraslan, L., de Graaf, A. J., Loot, A. E., Musson, R. E. A., Oosterhuis, W. P., Schuijt, M. P., van der Sijs, H., Verheul, R. J., de Wolf, H. K., Kusters, R., Hoedemakers, R. M. J., & Dutch Society for Clinical Chemistry and Laboratory Medicine, task group ‘SMILE’: Signalling Medication Interactions and Laboratory test Expert system (2019). Diagnostic error as a result of drug-laboratory test interactions. Diagnosis, 6(1), 69–71. https://doi.org/10.1515/dx-2018-0098
- National Library of Medicine. Daily Med [database]. https://dailymed.nlm.nih.gov/dailymed/
- Drugs.com. Find Drugs and Conditions [database]. https://www.drugs.com/drug_interactions.html