dietary supplements
Sean Cate
Sean Cate
February 25, 2024 ·  5 min read

13 Medication and Supplement Combinations That Should Avoided

Supplements are often taken to fill the gaps in our diet and support our overall health. However, it’s important to know that some supplements should not be mixed together due to potential interactions and reduced absorption. In this article, we will explore 13 supplement or medication combinations that should be avoided for optimal health.

Supplement Combinations to Avoid

Closeup photo of supplements with a white bottle
Source: Shutterstock

Magnesium and Calcium: Magnesium and calcium are essential minerals for overall health. However, when taken together, they can compete for absorption in the body.1 This means that both minerals may not be effectively absorbed, reducing their individual benefits. To maximize absorption, it is recommended to take any mineral supplements at least two hours apart.2 The combination itself is not dangerous, so if you are taking a supplement formulation containing the two, do not worry.

Zinc and Copper: Important minerals that play various roles in the body. However, zinc interferes with copper absorption. If you need to take both supplements, it’s best to space them out by at least two hours. High doses of zinc taken over a long period can also lead to copper deficiency, so it’s important to consult with a healthcare professional.

Iron and Green Tea: Iron is crucial for distributing oxygen to cells and maintaining energy levels. However, when taken together with green tea, iron absorption can be hindered. Green tea contains compounds that can decrease iron absorption. It is advisable to separate green tea and iron supplement combinations by a couple of hours to ensure optimal iron absorption.

Fish Oil and Ginkgo Biloba: Omega-3 fish oil supplements are known for their anti-inflammatory properties, while ginkgo biloba is claimed to support cognitive function. However, both fish oil and ginkgo biloba have blood-thinning properties. When taken together, they can increase the risk of uncontrolled bleeding or interfere with blood clotting. It is recommended to space them apart by at least two hours.

Read: B vitamins could help treat severe nonalcoholic fatty liver disease

Vitamins, Minerals, and More

Close up vitamins and supplements on white background with a brown bottle. Including Vitamin c, vitamin E, vitamin D3, salmon oil, fish oil and co enzyme Q10 capsules.
Source: Shutterstock

Melatonin and Sedating Herbs: Melatonin and sedating herbs like valerian, kava, and St. John’s Wort are commonly used for sleep support and relaxation. However, taking these supplement combinations can result in excessive sleepiness, as they have cumulative sedative effects. It is important to read the labels and be aware of the potential sleep-inducing effects of these supplements. You may find these combinations in off-the-shelf sleep formulas; however, these are usually dosed accordingly and should not cause excessive sleepiness. Consult with your healthcare practitioner before taking any new supplements.

Red Yeast Rice and Niacin: Red yeast rice and niacin are natural supplements used to lower cholesterol levels. However, supplement combinations like this do not increase benefits to your and may harm the liver. High doses of niacin, in combination with red yeast rice or prescription cholesterol-lowering drugs, can increase the risk of liver damage. It’s essential to be aware of potential side effects and consult with a healthcare professional.

Vitamins A, D, E, and K: Vitamins A, D, E, and K are fat-soluble vitamins that play important roles in various bodily functions. When taken together, vitamin K absorption may be reduced. To ensure optimal absorption, it is recommended to take vitamin K at least two hours apart from other fat-soluble vitamins. This is particularly important if you are K deficient and need extra K. Just like the magnesium and calcium if you are taking a supplement containing all of these (i.e., a multivitamin), it is not dangerous, and you do not need to discontinue its use. Multivitamins are convenient but are not ideal for the individual absorption of all the nutrients they contain.

Potassium and Calcium: Both potassium and calcium are essential minerals for proper bodily function. However, when taken together, they can compete for absorption, resulting in reduced absorption of each mineral. This means that you may not get the full benefits of potassium and calcium when they are taken simultaneously. It is advised to space them out by a few hours if you need to take both supplements.

St. John’s Wort and Antidepressants: St. John’s Wort is an herbal supplement often used for its potential antidepressant effects. However, it can interact poorly with other antidepressant medications. St. John’s Wort and certain antidepressants increase serotonin levels in the brain, which can lead to serotonin syndrome. This syndrome can cause severe symptoms such as muscle rigidity, seizures, fever, confusion, and anxiety. It is crucial to be cautious and inform your healthcare provider about supplement combinations and medications you are taking.

More Supplement Combinations To Avoid

Unrecognizable African Woman Taking Beauty Supplements For Glowing Skin, Holding Omega-3 Fish Oil Capsules In Hands, Side View
Source: Shutterstock

CoQ10 and Diabetes Medication: CoQ10 is a compound that supports heart health but can also lower blood sugar levels. If you are taking diabetes medications, combining them with CoQ10 can increase the risk of low blood sugar. Additionally, CoQ10 can lower blood pressure, and when combined with blood pressure medications, it can cause dangerously low blood pressure. Regular monitoring and close communication with your healthcare provider are essential when using these and medications.

Garlic and Blood Thinners: Garlic has natural blood-thinning properties. When taken with daily baby aspirin or blood thinners like Coumadin (warfarin), it can increase the risk of bleeding episodes and internal bleeding. It is crucial to inform your healthcare provider about all the supplement combinations and medications you are taking, as garlic is not the only supplement that can increase bleeding risk.

Vitamin K and Blood Thinners: Vitamin K is known for its role in blood clotting. However, when combined with blood-thinning medications, vitamin K can counteract their benefits. Foods rich in vitamin K, such as kale and broccoli, can also interfere with blood thinners. Echinacea, a popular cold remedy, may decrease the effectiveness of blood thinners and increase the risk of stroke. It’s important to be aware of these potential interactions and discuss them with your healthcare provider.

Antibiotics and Iron: Some antibiotics, particularly those in the tetracycline family, can interact with iron supplements, reducing the effectiveness of the antibiotics. To ensure optimal absorption of both antibiotics and iron, it is recommended to space out their intake. This helps to prevent potential interference and ensures that both medications are absorbed properly.

It’s important to note that the information provided is a general guide, and individual circumstances may vary. Always consult with a healthcare professional or pharmacist before starting any new supplement regimen or supplement combinations with medications to ensure personalized guidance and safety.

Keep Reading: Dietary Supplement Could Improve Cancer Treatment


  1. 13 Supplement or Medication Combos You Should Never Mix.” The Healthy. Denise Mann, MS. May 14, 2021.
  2. Vitamins & Supplements You Should Not Take Together.” Yahoo. Brianne Hogan. April 29, 2023.