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What Vitamins and Supplements Should Not Be Taken Together?

Published by Dr. Venn-Watson
Dr. Eric Venn-Watson’s Highlights
    • Could you be taking supplements that don’t work well together?
    • Some supplements inhibit the absorption of others and even cause potentially serious reactions.
    • Know what you’re taking and what you should avoid taking together. 

Medically reviewed by: Eric Venn-Watson, M.D.

Let’s be honest: there aren’t many of us who are getting all the vitamins and minerals we need in our diets. Even for those of us who do eat healthfully, there can be nutritional gaps due to dietary restrictions or allergies. 

If you’re deficient in a certain vitamin or nutrient there are two courses of action to help get what you need:

  • Make up for it in your diet by including more foods that contain that vitamin, nutrient, or mineral.
  • Take a supplement. 

For most, the supplement route is the easiest and most accurate way to know you’re getting everything you need, without committing to eating mass quantities of the same foods each day.

Seems like an easy fix, right? Normally, it is. However, there are a few caveats. 

For one, our bodies don’t absorb some compounds in supplements as well as they do when those same compounds are found in the foods that we eat. 

Second, there are some combinations of supplements that shouldn’t be taken together. The bioavailability of some vitamins and nutrients can be affected by others. This means you could effectively “cancel out” one of the supplements you are taking if you’re taking it with another supplement that prevents your body from absorbing it properly. 

You can also experience side effects from taking the wrong supplements together. Side effects can be minimal, like gastrointestinal discomfort, or can be severe, like not allowing your blood to clot properly. 

Let’s take a look at some of the most commonly used supplements that shouldn’t be taken together, and how you can take them effectively to make sure you get what you need without risking an adverse reaction to your overall wellness. We’ll also look at an alternative to taking multiple supplements by taking one that can help every aspect of your health. 

Zinc and Copper

Your body needs both zinc and copper for total immunity. Zinc and copper play integral roles in helping your body heal wounds. Zinc is found in oysters and meat like veal, beef, pork, and lamb. Copper is found in organ meats, but don’t worry if chicken livers aren’t your thing. You can also get copper in nuts, seeds, and even chocolate. 

If you have certain medical conditions, you might be deficient in copper, which means that taking zinc when you have a cold could be a bad idea. Zinc interferes with copper absorption, so if you’re taking a copper supplement and decide to take zinc because you’ve got a cold, you could end up getting less copper than you need. 

If you need to take both zinc and copper together, it’s best to take them about two hours apart to ensure your body is able to properly absorb them both without interference. 

Iron and Green Tea

You probably know someone who is iron deficient, or “anemic.” When your body is low on iron, you may feel lethargic and like you can never get enough rest. You may also notice that you get sick more frequently. 

Iron plays a major role in our immune health as well as helping keep our blood oxygenated to give us energy. Many people are iron deficient, and taking an iron supplement can help their bodies get the iron they need. However, taking green tea along with iron can nullify the iron supplement altogether. 

Green tea has been shown to decrease the efficacy of iron supplements, and conversely, iron can also weaken the health benefits offered by green tea. Green tea blocks your body’s ability to absorb iron. 

You can still drink your favorite afternoon macha while taking an iron supplement, but avoid taking a green tea supplement (a more potent form of green tea) with iron. 

Melatonin and Relaxing Herbal Blends

We all experience sleeplessness from time to time, and a small dose of melatonin can help you drift off to sleep a little easier. However, if you’re in the habit of enjoying a cup of kava tea before bedtime, you should avoid taking melatonin on top of it. 

In fact, if you take any type of sedating herbal blend like kava, St. John’s Wort, valerian, ashwagandha, or poppy, you shouldn’t take a separate melatonin supplement. You could end up feeling more sedated, and could wake up feeling lethargic and tired. 

Vitamins A, D, E, and K

Everyone loves a good multivitamin, but if you check your multivitamin labels you’ll notice that vitamin K is excluded. That’s because vitamin K inhibits the absorption of these other fat soluble vitamins. If you need additional vitamin K, you’ll need to get it from your food, or take a vitamin K supplement at least two hours apart from the time you take your multivitamin. 

Red Yeast Rice and Niacin

High cholesterol affects more than 93 million Americans, making it a serious epidemic in our nation. High cholesterol is a major health concern with real, life-threatening consequences. Having high cholesterol puts you at higher risk for heart attack and stroke. 

If you have high cholesterol, your doctor may recommend you take cholesterol lowering medication. If you’ve decided to try to lower your cholesterol with diet, exercise, and supplements, you may decide to take red yeast rice and/or niacin. 

While both red yeast rice and niacin can help support healthier cholesterol levels, they should never be taken together. When taken together, they can contribute to a condition called rhabdomyolysis, which causes the breakdown of muscle tissue and can lead to kidney and liver harm. 

Additionally, there’s no evidence that taking both niacin and red yeast rice together will actually help your cholesterol numbers any more than taking just one of them alone. If you’re taking a cholesterol lowering medication, you should avoid these supplements altogether. 

CoQ10 and Diabetes Medication

Diabetics rely on certain medications to help keep their blood sugar levels within normal range. Individuals with type II diabetes can also be at higher risk of developing high blood pressure, or hypertension

CoQ10 is a supplement that can help support healthy blood pressure levels, however it can also cause serious interactions with prescription blood sugar lowering medications. CoQ10 not only lowers blood pressure levels, it can lower blood sugar, too, causing a diabetic to experience dangerously low levels of both.

Fish Oil and Ginkgo Biloba

Unless you’ve been living off the grid, you know you need omega-3 fatty acids in your diet. You may even be supplementing by taking a fish oil capsule each day, despite the fishy aftertaste and unavoidable fish burps! 

Fish oil can help support heart health and healthy weight, but taking it with ginkgo biloba is a bad combination. Ginkgo biloba is often taken to help improve memory and cognitive function, but both ginkgo and fish oil have blood thinning qualities that make them a combination you should avoid. 

An Easier Combination

If all these combinations seem a little intimidating, you can always forgo the medicine mixing and focus on becoming healthier a little more traditionally. Diet and exercise can make a huge difference in how your body feels. Eating an array of lean meats, fruits, and vegetables can help ensure you’re getting the nutrients you need.

You can also seek out supplements that may help you avoid the need to take multiple herbal remedies for common health concerns. One such supplement is pentadecanoic acid, or C15:0.

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What is C15:0 and How Can it Help?

C15:0 is an odd-chain saturated fatty acid that an increasing body of research suggests may be the first essential fatty acid to be discovered in over 90 years. 

C15:0 has the ability to take care of your health on the cellular level, by:*

  • Strengthening cell membranes and making them sturdier to protect your cells
  • Boosting mitochondrial function, so your cells produce more energy, which means you feel healthier and more vitalized
  • Supporting a healthy metabolism
  • Supporting healthy immune responses

C15:0 can help you feel better and live better, but getting enough of it in your diet may be problematic. C15:0 is found mostly in whole fat dairy products like whole milk and full fat butter, which many people actively avoid.  

Thankfully, there is a solution. Fatty15 is a once daily supplement you can take to meet your body’s C15:0 needs.* It’s simple, easy, and doesn’t require any other supplements to help improve your overall health. 

You can grab a trial kit to experience these benefits for yourself. It’s risk-free and offers the ability to improve your general health and wellness.* 

Get off the supplement merry-go-round and reduce your risks from supplement combinations by using fatty15 to help improve your overall wellness.* 


Zinc and Copper Intakes and Their Major Food Sources for Older Adults in the 1994–96 | Oxford Academic

6 Continuing Survey of Food Intakes by Individuals (CSFII) | Oxford Academic 

Supplements & Vitamins Dangerous duos: 5 supplement combos to avoid | MDLinx 

High Cholesterol Facts | CDC 

Diabetes and Hypertension: Is There a Common Metabolic Pathway | NCBI 

Profile photo for Eric Venn-Watson

Eric Venn-Watson M.D.

Eric is a physician, U.S. Navy veteran, and Co-founder and COO of Seraphina Therapeutics. Eric served over 25 years as a Navy and Marine Corps physician, working with the special forces community to improve their health and fitness. Seraphina Therapeutics is a health and wellness company dedicated to advancing global health through the discovery of essential fatty acids and micronutrient therapeutics.

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