As blogged previously, weight loss supplements do not have evidence to support that they actually work to lose weight, and some have concerning side effects associated with them.  One thing we as doctors check on when prescribing medications is whether there could be any interactions with other medications, but these databases do not include most supplements.

So today’s question is: Can weight loss supplements interaction with prescription meds?

A recent review addresses this question.  They looked at data on some of the most commonly used ‘weight loss’ supplements, including:

  • Beta glucans (fiber supplement)
  • bitter orange (a stimulant)
  • capsaicin (derived from chili peppers)
  • carnitine
  • chitosan (found in the exoskeleton of crustaceans and insects)
  • chromium
  • conjugated linoleic acid (a fatty acid)
  • fucoxanthin (a marine carotenoid)
  • Garcinia cambogia
  • glucomannan (a fiber from the Konjac root)
  • guar gum (derived from a plant)
  • Hoodia gordonii
  • Irvingia gabonensis (fiber from a seed)
  • raspberry ketone


For almost every one of these agents, there is a list of potential drug interactions with prescription medications, including:

  • decreased levels/efficacy of the prescription medication
  • increased levels/efficacy of the prescription medication (eg, too much effect of blood thinners, too much blood sugar lowering effect of diabetes medication)
  • increased risk of medication-induced side effects


The reasons for the drug interactions range from an effect of the supplement to interfere with absorption of prescription medications, to the supplement inhibiting or overstimulating the liver enzymes that metabolize medications, to antagonizing the action of the medication.


Reciprocally, some medications can affect metabolism of some supplements as well, potentially increasing the risk of side effects of the supplement.


The list of medications that can be affected by supplements is long, including (but not limited to):

  • diabetes medications
  • blood pressure medications
  • anti inflammatories (including aspirin, ibuprofen)
  • thyroid hormone
  • antidepressants
  • blood thinners


It is important to tell your health care provider what supplements you are taking, so that any known concerns can be identified.   However,  because most supplements have very little data available, we most often cannot say whether a supplement is safe.


As the authors note:

“Many bioactive constituents (of supplements) remain unknown, uncharacterized, or not adequately tested…, possibly shifting their risk-benefits balance against their use.”


Dr Sue Pedersen © 2019 

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