Do Multivitamins Have Drug Interactions?

In our latest question and answer, the pharmacist discusses medications that could potentially interact with multivitamins.

Do Multivitamins Have Drug Interactions?
May 08, 2019

Tammy asked

I used to take multivitamins daily but stopped taking them for fear of drug interactions. I would like to know if there are any suspected drug interactions I should know of and/or if it is safe to begin taking them? I was looking at a 'women over 50 multivitamin' and the GNC "Women's Ultra Mega 50 Plus" multivitamin, which has extra ingredients in it for memory etc...I do take hydrocodone 10-325 daily. Advice?

At a glance

  • Many of the ingredients in multivitamins (e.g. calcium, magnesium and zinc) can significantly decrease the absorption of a variety of prescription drugs. Be sure to let your pharmacist and doctor know everything you are taking (including prescription, over the counter and herbal products).


Pouring Multivitamins In Hand With Text - Multivitamin Drug Interactions

Drug interactions between multivitamins and prescription medication aren't overly common, but they certainly do exist and are important to be aware of.

The most significant interactions come from some of the active ingredients in multivitamins negatively affecting the absorption of certain drugs.

A wild card in this is that there are so many different brands of multivitamins available over the counter, and they all contain different ingredients.

Additionally, many of them contain ingredients beyond vitamins and minerals.

Many ones that are specifically marketed towards men or women contain herbal ingredients that are well-known to have numerous interactions.

For example, a 'women over 50' multi-vitamin may contain black cohosh, an herbal ingredient used to reduce the symptoms of menopause. It has been linked with increasing the risk of liver toxicity when taken with statin cholesterol medications.

For another example, many 'men over 50' products contain saw palmetto, purported to help reduce the symptoms of BPH (benign prostatic hyperplasia). It may interact with androgens and other hormone-containing products.


Assorted Pile of multicolor pills and capsules

It is nearly impossible to list all the potential interactions multivitamin products may have with prescription medication due to the sheer number that are available on the market.

Most contain similar ingredients (e.g. iron, calcium, vitamin B6, etc...) but can vary in the addition of other nutrients.

If you have a question about a specific multivitamin product, be sure to ask one of our pharmacists and we can provide some more specific information.

Nevertheless, below are some of the most common interactions between multivitamin products and prescription drugs.


Synthroid (levothyroxine) is a thyroid replacement hormone medication.

It is well-known to significantly interact with not only other medications but food as well.[1]

All of the following can significantly decrease Synthroid absorption:

  • Calcium salts (e.g. calcium carbonate, calcium citrate)
  • Iron salts
  • Chromium (e.g. chromium picolinate)
  • Aluminum
  • Magnesium salts

A decrease in Synthroid absorption due to anything from the above list is mostly due to 'chelation', a process in which metal ions bind to molecules (like Synthroid). This creates an unabsorbable complex.

A decrease in thyroid hormone absorption (from Synthroid) could potentially cause hypothyroidism, with symptoms including:

  • Lethargy
  • Feeling of cold
  • Weight gain
  • Brittle hair and nails

Not only can Synthroid absorption be affected by many of the ingredients in multivitamins, but any iodine contained in them could also potentially affect thyroid hormone levels.

Since so many of the ingredients in multivitamins can interact with Synthroid, it is recommended to separate administration of both by at least 4 hours.[2]

Tetracycline Antibiotics

Just like the interaction with Synthroid, several ingredients in multivitamins can chelate to tetracycline antibiotics, forming insoluble compounds.[3]

Most studies report that with calcium specifically, a significant decrease in tetracycline absorption occurs if taken within 60 minutes of each other.[4]


Bisphosphonates are drugs used for the treatment and prevention of bone fractures. The class includes:

Similar to most other drug interactions involving multivitamins, products that contain ingredients like calcium and magnesium need to be separated from bisphosphonate by at least 30 to 60 minutes to avoid a significant decrease in absorption.[5]


Not only can some ingredients in multivitamins decrease absorption of digoxin (like magnesium), others (like calcium) can increase the overall effects of it. This increases the risk of serious adverse effects.[6]

Quinolone Antibiotics

Just like tetracyclines, quinolone antibiotics are well known to have a decrease in absorption if taken along with many of the ingredients found in multivitamins.[7]


Studies show that zinc, a common component in multivitamins, can significantly decrease the absorption of Keflex (cephalexin).

In fact, one study found that taking zinc sulfate with cephalexin 500 decreased maximum concentrations of cephalexin by 31% and reduce the overall exposure of the drug by 27%.[8]


Aside from the common vitamins and minerals contained in multivitamins, many contain herbal products.

There isn't much data available for a lot of the herbal products on the market in regard to any interactions they may have, but they certainly exist.

You mentioned a product you were looking at that had additional ingredients for memory (most likely ginkgo biloba).

Ginkgo biloba has been reported to interact with numerous medications, including blood thinners and drug metabolized by the liver metabolizing enzyme CYP3A4.[9]

It is important to look at all the ingredients in your multivitamin product and check them for potential drug interactions.

Final Words

The above list of interactions is only a small sampling of ones that exist.

The main point here is that, even though multivitamins are available over the counter and widely consumed, we sometimes underestimate their ability to be involved in significant drug interactions.

It is important to ensure both your pharmacist and doctor know all of the medication you take so they can properly evaluate the risk for interactions.

You asked in your question about hydrocodone products so to answer that specifically, there are no known interactions with most multivitamin products (as far as we know).

  1. ^ Synthroid Prescribing Information. AccessFDA
  2. ^ Elsevier ClinicalKey: Synthroid Monograph. ClinicalKey
  3. ^ Interactions with the absorption of tetracyclines. PubMed
  4. ^ Elsevier ClinicalKey: Tetracycline Monograph. ClinicalKey
  5. ^ Fosamax Prescribing Information. AccessFDA
  6. ^ Digoxin Prescribing Information. AccessFDA
  7. ^ Drug interactions with quinolone antibacterials. PubMed
  8. ^ The effect of staggered administration of zinc sulfate on the pharmacokinetics of oral cephalexin. PubMed
  9. ^ Pharmacokinetic drug interactions involving Ginkgo biloba. PubMed

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