April 09, 2020

What Vitamins Should Not Be Taken Together?

Everyone knows you should take your vitamins. It has been drilled into us since we were kids. The modern food supply chain is excellent at feeding large amounts of people every day. Still, its development required a massive agricultural overhaul that has led to much of the world's crops being grown in nutrient-poor soil.  

For this reason and others unique to overall health, many people are advised by their physicians to supplement the nutrients they get in their daily diets with extra vitamins and minerals. People who practice a restricted diet like vegans and vegetarians may have a particular need.

Pregnant women have different needs. However, for all the unique and personal aspects that determine your health and wellness regiments, anyone taking vitamins should be keenly aware of which vitamins you cannot bring together. While vitamins are mostly safe, being mindful, and informed about their potential pitfalls is essential. 

Why You Shouldn’t Take All Vitamins Together?

Generally, if you take a common multivitamin and eat a reasonably healthy diet, then odds are you shouldn't have to worry about any vitamin interactions. It is when you're taking specific vitamins that you have the highest risk of adverse interactions. 

However, like many things in life, vitamins, and how you take them can get unduly complicated. This is because each person receives different amounts of vital nutrients from their healthy diet.

If you then add pre-existing and genetic conditions that can change how the body processes nutrients, then you end up with a list of different needs from vitamins that is almost as unique as someone's finger-print. 

Unfortunately, for reasons partially economic and partially due to a lack of robust regulatory framework, the industry selling vitamins tends to peddle a one-size-fits-all approach that does not match the unique realities of how the human body absorbs and processes vital nutrients.

It is important to note that all the below vitamins can be taken in a healthy way that will result in a more well-rounded nutrition profile. However, the below interactions and effects of mixing vitamins should always be carefully considered before making any change to your daily regiment. Here's the list of vitamins you shouldn't take together:

List Of Interactions & Effects Of Mixing Vitamins

Calcium and Vitamin D

Calcium and Vitamin D supplements have been given for bone health, particularly in women with a risk of osteoporosis. A study in the Annals of American Medicine suggested that taking these dietary supplements together over time can lead to a slight increased risk of stroke. The finding was based on data from the Women’s Health Initiative.

While there is some controversy around these findings, it is essential to be aware of the potential risks. It is also crucial for women who are at risk of bone issues to still find another way to supplement their bone health, even if this method may lead to increased risk of stroke, there are other ways to fortify the skeletal structure.

Niacin Combinations and Cholesterol

Niacin is generally safe. However, if you are taking certain anti-cholesterol prescription medications, an adverse reaction is possible. The medicine simvastatin won't work appropriately in raising HDL cholesterol if you are taking too much niacin. This effect has only been documented in patients who have coronary artery disease or poor heart health. Niacin is present in many multivitamins. 

Folate Supplements and Vitamin B 12 Deficiency

Folate and Vitamin B 12 are both very commonly used vitamin supplements.  Folate is particularly important for pregnant women to take. Older folks, vegans, and those with severe gastrointestinal disorders are usually those told to regularly take B12 supplements. 

While both of these dietary supplements can be taken together safely, there is a unique problem that can develop. The folate can mask a vitamin B12 deficiency in testing. A lack of B vitamins can lead to severe consequences like anemia.

The problem is that folate will treat the anemia, but it will not address the underlying vitamin deficiency. So what primarily happens is that you can have a vitamin deficiency in B12 but not know it because the folate interferes with the testing. This, it has been found, can lead to permanent nerve damage. 

If you're an individual that is at risk of a vitamin B12 deficiency (particularly if you're a vegan), then you should be wary of this potential interaction and always ask for medical advice from your health care professional. 

Vitamins K and E and Blood Clotting

Vitamin K is vital in the body's process of blood clotting. If you are taking a Vitamin K supplement, then you have to make sure to control your intake of vitamin E. This includes checking any multivitamins that contain vitamin E. This is because high levels of Vitamin E will offset any benefit that you will get from your Vitamin K supplement. 

Another thing to keep in mind is that for those taking anti-clotting prescription medications like warfarin. Vitamin E will interfere with the mechanism that causes this medication to work. If you are on a blood thinner, then it is essential for you to bring them into any decision to take any vitamin supplements. 

This is a particularly vital reaction to monitor and pay attention to. Interference with the goals of blood-thinning and blood pressure medications can result in serious health consequences up to and including death. 

Calcium and Iron Absorption

Anemia from iron deficiency is the most common form of anemia. This condition can result from a diet lacking in iron-rich foods and can be corrected both by altering diet or by taking a supplement. Foods high in iron include beef, beans, dark green leafy vegetables and other meats. 

According to the National Institutes of Health (NIH), taking a calcium supplement can interfere with your body’s iron absorption. So if you are taking a calcium and iron supplement at the same time, you may be altogether canceling the effect of the iron supplement.

However, this problem can usually be easily solved by only taking your iron and calcium supplements a few hours apart or on alternating days. 


Though most multivitamins are considered safe, you should always pay close attention to what you multivitamin contains. Many multivitamins, maybe most, contain some of the above-mentioned compounds. If you're taking multiple supplements, it is still possible to get one of the above interactions from the contents of multivitamins.

Make sure you're taking multivitamins that do not contain more than 100% of your daily needs for any of the vitamins they contain. If your doctor directs you to take any vitamin or supplement in high doses above the recommended daily value, be sure to be extra wary of any of the above interactions. 

What To Be Aware of When Seeking Vitamins

Although vitamins are largely considered safe, there are still things any informed consumer should be aware of before purchasing them. The Food and Drug Administration (FDA) which regulates the contents of medicine and food in the United States to ensure purity and to prevent contaminants from entering these necessities.

Vitamins are regulated as a supplement. What this effectively means is that the Federal Government does not verify the claims made by Vitamin sellers or the contents of their products.

Fear not, there are many private methods for finding the best vendors in the space. Make sure to vet the company you’re purchasing your supplements from. Make sure they can independently verify the contents of their supplements. 

Always make sure to check with medical professionals when integrating a supplement into your health and wellness routine. While the above interactions are the most common and well-understood, specificities to each person's individual health and body may significantly affect interactions of vitamins.

In other words, if you have a health condition that sets you apart, vitamins may not work the same way on your body the way they do on others. 

Who Should NOT Take Vitamins and Supplements?

Some people who have underlying health conditions should avoid vitamins unless specifically recommended by a physician. While vitamins are mostly a good thing and good nutrients for our body, sometimes too much can cause serious problems.

  • Pregnant and breastfeeding women should avoid specific vitamin supplements and mineral supplements. They should only be taking prenatal vitamins specifically made for women during their pregnancy and approved by their physician. 
  • People who take certain heart medications should avoid vitamin supplements and dietary supplements because of adverse interactions.
  • People who have an immediately pending surgery should avoid many vitamins. Some vitamins can cause excessive bleeding in these situations. 
  • People who have had cancer or are being treated from it. Ironically, the beneficial aspects of vitamins can also sometimes assist cancer cells in growing. 

These guidelines are, of course, general, and can at any time be overridden by the advice of your primary care physician. If there is one thing to glean from this article, it is that everybody's vitamin needs are quite different.

You cannot rely on general information to construct your vitamin regiment. It is much safer to consult your physician. If possible and financially feasible, it is also best to get a micronutrient test from a certified nutritionist to determine exactly what deficiencies you may be experiencing. 

Image by Roman Kraft/Unsplash

This article is based on scientific research and/or other scientific articles and contains trusted sources.

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