6 Vitamins & Supplements You Should Not Take Together

You know the drill: You have a ton of vitamins to take in a day but you’re not sure exactly when (or really if) you should take them all. And, while while it’s always preferable to get our vitamins and minerals from food, sometimes vitamin supplementation can help us fill the gaps in our diet. So here you are with your chosen vitamins (which should be properly prescribed or recommended by a medical professional) and you don’t know the best strategy for taking them.

One reason behind the confusion? Some supplements simply don’t play nice together. In some cases, the amount of a vitamin your body is able to absorb depends on which other supplements you might be taking at the same time. Plus, taking some supplements concurrently may result in adverse interactions, which can be harmful to your health.

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It’s also important to note that you should always talk to your doctor before starting a new supplement (even if it’s “just” a daily multivitamin!), and make sure to read the information packet on any new prescription you receive — it should list out any supplements that trigger adverse interactions with the medicine. With that said, keep reading to learn about some common supplements you shouldn’t take together.

Magnesium and calcium/multivitamin

Many people like to take magnesium in the evening, as it can promote a sense of calm and supports muscle relaxation. But if you do take magnesium, Erin Stokes, naturopathic doctor and medical director at MegaFood, recommends not taking it at the same time as your multivitamin, as it may interfere with the absorption of smaller minerals found in the multivitamin, like iron and zinc. Additionally, she says to refrain from taking calcium, magnesium, or zinc together as they will “compete for absorption.”

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However, both magnesium and calcium may be helpful supplements to take separately because they can help prevent osteoporosis, Jaydeep Tripathy, a senior resident in the Department of Radiology at Kamakshi Hospital, tells SheKnows. In order to maximize the benefits, make sure to take them two hours apart.

Vitamins D, E, and K

“Studies have shown that a person’s absorption of Vitamin K may be reduced when other fat-soluble vitamins such as Vitamin E and Vitamin D are taken together,” Chris Airey, a GMC-registered doctor in the UK and medical director at Optimale, tells SheKnows. “It’s advised that you take these vitamins at least 2 hours apart to maximize your absorption.”

These vitamins won’t produce harmful interactions, but Dr. Airey says it’s “simply not efficient” to take them together, as your body’s ability to absorb the vitamins will be reduced if you take them all at the same time.

Fish Oil and Gingko biloba

Omega-3 fish oil supplements are great for heart health and gingko biloba has cognitive benefits, according to studies. Both can be helpful supplements to take, but not at the same time, according to Dr. Tripathy, because they have blood-thinning potential and “taking both together can increase risk for uncontrollable bleeding or inability to clot.”

Copper and zinc

If you are taking copper supplements because of copper deficiency, avoid taking zinc at the same time, says Dr. Airey. “Zinc can help to boost the immune system but can interfere with your body’s absorption of copper. If you must take both, take them at least two hours apart.”

Signs that you are still dealing with copper deficiency include fatigue, weakness, brittle bones, cold sensitivity and easy bruising.

Iron and green tea

No, green tea isn’t a supplement, but it is a soothing, antioxidant-infused beverage that many of us enjoy and which may have beneficial effects on both blood pressure and cholesterol, according to the National Center for Complementary and Integrative Health (NCCIH). Unfortunately, taking iron supplements along with green tea isn’t a good mix.

“Green tea can actually cause iron deficiency if taken in large quantities for longer periods of time,” says Dr. Tripathy. “Iron, on the other hand, can decrease the efficacy of green tea.”

The solution? Skip green tea on days when you’re taking your iron supplement and decrease your weekly consumption.

Vitamin C and B12

According to Dr. Airey, some studies have shown that Vitamin C could break down Vitamin B12 in your digestive tract, reducing your B12 absorption. While some studies dispute this, it’s still a good idea to wait at least two hours before taking Vitamin C with your Vitamin B12.

“Vitamin B12 plays an important role in red blood cell production and the proper functioning of your nervous system,” Dr. Airey explains, “and B12 deficiency can lead to poorer nerve health and affect red blood cell development and function.”

How to Safely Mix Supplements

Mixing supplements can be overwhelming at first, so make sure to always ask your doctor for clarification on the specific medicine and vitamins you’re taking. Every time you go in for a check-up, fill them in on the supplements you take to make sure your chart stays up to date.

From there, Stokes says the most important aspect of a supplement regimen is to keep it simple and set yourself up for success. “For example, I always take my multivitamin and turmeric supplements in the morning, and take my magnesium and probiotic in the evening,” she explains. “That’s the basic schedule. Depending on the season, I may add in extra zinc and vitamin D3, which I take with lunch. Once you get into a routine, and know what to take when, it just becomes part of your daily habits. It doesn’t have to be complicated.”

A version of this story was published March 2021.

Looking to level-up your post-workout self-care? Check out our favorite recovery essentials.


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