What Vitamins Should Not Be Taken Together 2025 Update

All vitamins are important for health, each with its own contribution to your body. Some are essential nutrients that the body needs, but it’s also important to know what vitamins should not be taken together. It is possible to overdo it, which can affect the absorption of another vitamin or cause a negative interaction with medications. 

Often foods can provide exactly the amounts that your body needs. The problem usually arises with taking supplements that are above the Recommended Daily Allowance (RDA). 

Water-soluble vitamins are not as much of a concern as any excess is excreted from the body. However,  fat-soluble vitamins like vitamins A, D, E, and K can accumulate in the liver to toxic levels if consumed in excess.

In addition to the potential to overdo it on vitamins, different vitamins can interact with each other, which can cause side effects and affect their absorption. 

What Vitamins and Supplements Should Not Be Taken Together

Vitamin A

Vitamin A^[1] is one of the fat-soluble vitamins and is the vitamin most important for your vision. Without it, you can go blind. Luckily, this is now a rare and preventable illness. You can find vitamin A in dairy products, eggs, fish, and organ meats. 

Vitamin A is important for the immune system, embryo development, and expression of genes (what makes a person look a certain way or have certain traits passed on from family). It also supports the production of mucus-forming cells and cells that help with vision and promotes heart, eye, lung, and ear development^[2].

The recommended dosage^[1] is measured as micrograms (mcg) of RAE (retinol activity equivalent); this RAE is done to account for the differences in different retinoids. The dosage for females over 18 is 900 mcg RAE and for males is 700 mcg RAE.

Vitamin interactions	Effects and Symptoms
Vitamin A-rich foods-beta carotene[3]	Can cause hyperpigmentation of the skin; for example: eating a lot of carrots can cause the skin to turn orange temporarily.

Supplement interactions	Effects and Symptoms
Vitamin A Supplement with Vitamin A rich foods[4]	Severe headache, blurry vision, nausea, dizziness, dry skin, painful muscles and joints, feeling tired, depressed, and abnormal liver lab results.

Medications interactions	Effects and Symptoms
Soriatane®[5]	Increases the risk of vitamin A to toxic levels; severe headache, blurry vision, nausea, dizziness, dry skin, painful muscles and joints, tiredness, depression, and abnormal liver lab results. In some severe cases, cerebral spinal fluid pressure can lead to coma and death.
Targetrine®[5]	Increases the risk of vitamin A toxic levels; severe headache, blurry vision, nausea, dizziness, dry skin, painful muscles and joints, tiredness, depression, and abnormal liver test results. In some severe cases, cerebral spinal fluid pressure can lead to coma and death.
Alli®[5]	Decrease absorption of vitamin A; deficiency of vitamin A can lead to night blindness and can lead to permanent blindness, abnormal lung development, increased risk of infections, and anemia.
Xenical®[5]	Decrease absorption of vitamin A; deficiency of vitamin A can lead to night blindness and can lead to permanent blindness, abnormal lung development, increased risk of infections, and anemia.

Recommendation: Intake of vitamin A should always come from food first; three good sources are beef liver 3oz, one whole baked sweet potato, and ½ cup of boiled spinach. If the source from food is not enough, say due to food preferences taking a multivitamin that includes vitamin A under 100% of the daily value can be beneficial. Anything more than 100% of the daily value can lead to toxicity levels.

Vitamin B

The group of B vitamins is all considered water-soluble vitamins. There are 8 essential B-vitamins that are not made by the body: vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), B12 (cobalamins). 

These vitamins are important in cell metabolism and the making of red blood cells. Each one has specific functions as well as shared functions with other nutrients. 

Vitamin B1 (Thiamine)^[6]:

• Helps release energy from carbohydrates
• Dosage: Men 1.2 mg/day and Women 1.1mg/day

Vitamin B2 (Riboflavin)^[7]:

• Helps the breakdown of fatty acids
• Dosage: Men 1.3mg/day and Women 1.1mg/day

Vitamin B3 (Niacin)^[8]:

• Helps in the energy transfer of sugar, fat, and alcohol
• Dosage: Men 16mg NE and Women 14mg NE (Niacin Equivalent)

Vitamin B5 (Pantothenic acid)^[9]:

• Helps in the function of fatty acids and carbohydrates
• Dosage: Men 5mg/day and Women 5mg/day

Vitamin B6 (Pyridoxine)^[10]:

• Is part of making neurotransmitters
• Dosage: Men 1.3mg/day and Women 1.3mg/day

Vitamin B7 (Biotin)^[11]:

• Helps in the metabolism of fats, protein, and carbs
• Dosage: Men 30mg/day and Women 30mg/day

Vitamin B9 (Folate)^[12]:

• Is needed for normal cell division
• Dosage: Men 400mcg/day DFE and Women 400mcg/day DFE (Dietary Folate Equivalent)

Vitamin B12 (Cobalamin)^[13]:

• Is essential in making red blood cells in the bone marrow
• Dosage: Men 2.4mcg/day and Women 2.4 mcg/day

Vitamin interactions	Effects and Symptoms
Vitamin B9 and Vitamin B12	Excess Vitamin B9 (folate or folic acid) may mask Vitamin B12 (cobalamin) deficiency[14].
Vitamin C and Vitamin B12	Vitamin C may reduce the absorption of vitamin B12[15]

Supplement interactions	Effects and Symptoms
Vitamin B7 (biotin) and Biotin dietary supplements	May interfere with lab testing, affecting diagnosing of medical conditions.
Vitamin B3 (niacin) and niacin dietary supplement	Excess intake can cause flushing of the skin, burning, tingling, and itching sensations.

Medications interactions	Effects and Symptoms
Vitamin B3 and Rifater®[8]	Niacin production from tryptophan can be interrupted.
Vitamin B7 and anticonvulsants[16]	Anticonvulsants can reduce biotin levels
Vitamin B12 and Metformin[17]	Vitamin B12 deficiency
Vitamin B12 and Gastric Acid Inhibitors[18]	Vitamin B12 deficiency

Recommendation: The eight essential B vitamins are varied, and you can get these vitamins in almost all fruits, vegetables, legumes, and some meats. That is why a varied diet can help you get a little bit of each, reducing the likelihood of needing to supplement. 

But if you still want to supplement, a multivitamin can help get a little of each. As long as the daily value percentage does not exceed 100%.

Vitamin C

Vitamin C^[19] is a water-soluble vitamin important for making collagen, an important part of connective tissue that aids in h wound healing. It also makes certain neurotransmitters, builds protein, acts as an antioxidant, and may help keep the immune system healthy. 

You can get this vitamin through citrus fruits like oranges, limes, lemons, and tomatoes.

The recommended dosage for males is 90mg/day and 75mg/day for females. 

Vitamin interactions	Effects and Symptoms
Vitamin C and Iron	Excess vitamin C may cause increased iron absorption; it usually happens to people with hereditary hemochromatosis.

Supplements interactions	Effects and Symptoms
Vitamin C and Iron supplement	Iron supplements with excess vitamin C can exacerbate iron absorption[20] and lead to reduced zinc absorption. Also, gastritis and gastric lesions may occur.

Medications interactions	Effects and Symptoms
Vitamin C and Statins (Zocor®)[21]	This combination of vitamin C and statins may reduce the function of statins role in increasing high-density lipoprotein levels.

Recommendation: You can get vitamin C in fruits and vegetables, especially in citrus fruits. The top three sources of vitamin C are ½ cup of sweet red bell pepper, ¾ cup of orange juice, and one medium orange. The advantage of consuming vitamin C through foods is that you can eat these foods raw and obtain the nutrient. 

Vitamin C can also be obtained through supplementation and can best be taken through a multivitamin that does not exceed 100% of the daily value, any more than that; the body will just expel the excess. 

Vitamin D

Vitamin D^[22] is a fat-soluble vitamin that is most commonly made by the skin through sun exposure. You can also get your daily dose from food sources and dietary supplements. 

When taken in excess, it can lead to toxic levels. Usually, the excess intake is from a combination of foods and dietary supplements rather than from sun exposure.

A deficiency of vitamin D can impact heart health^[23] and negatively affect blood pressure^[24]. 

The recommended dosage for both males and females is 100mcg/day. Vitamin D is found in enriched foods like cow’s milk, the flesh of fatty fish, and ready-to-eat cereals. 

Vitamin interactions	Effects and Symptoms
Vitamin D and Calcium[25]	Moderate vitamin D increases calcium absorption; added with high calcium may lead to an increased risk of kidney stones.

Supplements interactions	Effects and Symptoms
Vitamin D-rich foods and Vitamin D supplements	May increase calcium absorption[26], causing nausea, and vomiting, muscle weakness, pain, loss of appetite, excess thirst, and possible kidney stones[25].
Vitamin D and Calcium	High calcium supplements can increase the risk of kidney stones[25].

Medications interactions	Effects and Symptoms
Orlistat®[27]	Orlistat with a fat-reduced diet may decrease vitamin D absorption
Statins[28]	Reduce cholesterol, therefore may also reduce the making of vitamin D.
Thiazide diuretics[28]	May increase calcium absorption, causing hypercalcemia.

Recommendation: Vitamin D is special in that part of the source is a collaboration between the sun and the skin, but you can also obtain vitamin D through food sources. The top three sources are 1 tbsp of cod liver oil, 3oz of farmed cooked trout, or 3oz of cooked salmon. Other vegetable sources of vitamin D or fortified foods are also possible but in fewer amounts. 

Supplementing with vitamin D is also possible, although you can find foods fortified with vitamin D^[29] like cow’s milk, plant-based milk alternatives, ready-to-eat breakfast cereals, juice, yogurt, and margarine. 

Vitamin E

Vitamin E^[30] is another fat-soluble vitamin important for the immune system. It helps dilate blood vessels and delays blood clotting. It is found naturally in foods, in fortified foods, or as a dietary supplement. 

It’s an antioxidant that can help prevent damage from free radicals in the body and unstable molecules that can affect our health. It also may help reduce the risk of coronary artery disease, though more research is needed^[30].

The recommended dosage for males and females is 15mg/day. You can find vitamin E in nuts, seeds, vegetable oils, green leafy vegetables, and fortified cereals.

Vitamin interactions	Effects and Symptoms
Vitamin E, Vitamin C, selenium, carotene (combination of antioxidants), and Vitamin B3 (niacin)[21] with Simvastatin	The combination of antioxidants vitamins E and C with Selenium and beta-carotene; while vitamin B3 is used in combination with the medication Simvastatin (Zocor®) can lead to the stunting of the rise of healthy high-density lipoprotein.

Supplements interactions	Effects and Symptoms
Vitamin E[30] supplements	Excess intake of vitamin E in supplement form can cause hemorrhage and interrupt normal blood coagulation.
Vitamin K[31] supplements	Excess vitamin E and K can interfere with blood clotting.

Medications interactions	Effects and Symptoms
Coumadin®[33]	Can increase the risk of bleeding
Statins[21]	Stunt the rise of the healthy high-density lipoprotein

Recommendation: Sources of Vitamin E can be first obtained through foods, the top three sources are 1tbsp. Of wheat germ oil, 1oz of dry roasted sunflower seeds, and 1oz of dry roasted almonds. Other sources can also be vegetables in lower quantities. Although the idea is that if you have a variety of each food, you can obtain an adequate amount. 

Vitamin K

Vitamin K^[31] is a fat-soluble vitamin, but unlike other fat-soluble vitamins, this vitamin has a low potential for toxicity. It’s known as the blood-clotting vitamin, as it helps your body properly clot the blood to help close wounds. It does this by making the protein that helps with blood clotting. 

Because of this, Vitamin K can often interact with blood-thinning medications in excess and render them less effective. 

The recommended dosage for vitamin K for males is 120mcg/day and 90mcg/day for females. Green leafy vegetables are one of the best vitamin K sources.

Vitamin interactions	Effects and Symptoms
Vitamin K and Vitamin A	Excess vitamin A can reduce the absorption of vitamin K.

Supplements interactions	Effects and Symptoms
Vitamin K supplement	It may affect blood-thinning medications
Vitamin E[30] supplement	Excess vitamin E and K can interfere with blood clotting.

Medications interactions	Effects and Symptoms
Coumadin®[33] (Blood thinners)	Vitamin K clots the blood and may reduce coumadin’s (warfarin) function as a blood thinner.
Antibiotics[34]	Antibiotics may wipe out vitamin-K-producing gut bacteria and inhibit vitamin K function in the body.
Orlistat and Coumadin® use[35]	Can reduce the absorption of vitamin K

Recommendation: Good sources of vitamin K can be found in green leafy vegetables, fruits, and some vegetable oils, and other lower sources are dairy products and meats. Three good sources of vitamin K are ½ cup boiled collards, ½ cup turnip greens, and ½ cup boiled spinach. 

This is the one vitamin that can seriously affect the function of medication and like vitamin K with Coumadin®, speaking with a Registered Dietitian can help you figure out the amount of vitamin K-rich foods you can have without it affecting the medication.

Things to Do If Vitamin Toxicity Occurs

If you’re concerned about vitamin toxicity, the first thing you need to do is talk to your doctor. Have them evaluate the medication your doctor prescribes with all your over-the-counter supplements and do a food recall to identify the source of vitamin toxicity. 

How to Take Vitamins Safely

Before taking any new dietary supplements, it’s important to look at your current over-the-counter supplements to make sure they don’t exceed the Daily Value percentage. You may already be taking a supplement that meets your daily needs without even knowing it.

When choosing herbal supplements, make sure you check your current medications and speak to your doctor or pharmacist. Some herbal supplements reduce the absorption of medications. 

To obtain essential vitamins without having to keep track of individual supplements, you can choose multivitamins or prenatal vitamins that usually have a variety of vitamins and minerals that often don’t have high doses of vitamins and minerals. 

Always follow the manufacturer’s dosage instructions on the label of the supplement to avoid overdosing and check the label for all ingredients and warnings. 

What to Look for When Taking Multivitamins

When choosing multivitamins, take into consideration the type you are looking for. A multivitamin can be made for children, pregnant women, men, women, older adults, or people with medical conditions that may have a deficiency. 

Pregnant women should choose folate supplements that include iron, vitamins C and D, and calcium. On the other hand, older adults should choose multivitamins that specifically include calcium and vitamin D supplements.

A person with gastrointestinal disorders like gastritis can get an upset stomach easily and may need to choose multivitamins that aren’t taken on an empty stomach. 

Other things to look out for are the adverse interactions of vitamin interactions or mineral interactions in multivitamins. For example, some minerals compete for absorption if there is an excess of any particular mineral.   

Elevated zinc levels in the body can interfere with copper absorption and can even lead to copper deficiency. Deficiency in copper^[36] can lead to symptoms of anemia, high cholesterol, connective tissue disorders, osteoporosis, and overall bone health.

What are Positive Vitamin Interactions?

On a positive note, some vitamins should go together, and even minerals and mineral supplements can go together. When certain vitamins work as a team, they benefit the body’s ability to process other nutrients. 

With an iron deficiency, iron-rich foods that include vitamin C are typically recommended to increase iron absorption^[37]. With a diet that is low in iron-rich foods or low in vitamin C, adding a vitamin C supplement may be beneficial to increase iron absorption^[38]. 

Calcium and vitamin D are great partners; having an adequate amount of vitamin D can help calcium more effectively^[39]. 

A calcium deficiency^[40] can occur if a person has lactose intolerance, cow’s milk allergy, or is vegan. Taking calcium through animal or plant-based foods or a calcium supplement can also help with bone health and the prevention of osteoporosis.

Summary

Obtaining all of your essential nutrients through food is the best way to go. Many vitamins that you naturally get from foods will already be in balance and may not cause negative interactions. 

Understandably, it’s not always possible to get in enough nutrients through your diet alone.  But certain vitamins can come in exceedingly high doses when consumed in supplement form. The benefits may outweigh the risk of taking vitamins in supplement form when you are in need, but it does not mean you shouldn’t be aware of any possible interactions.

When taking prescribed medications, always communicate with your doctor regarding any over-the-counter supplements and herbs you are consuming to help reduce the possibility of toxicity.

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