What vitamins and supplements should not be taken together?

What vitamins and supplements should not be taken together?

Not enough people realize that not every vitamin and supplement can and can be taken together. Supplement timing is a critical factor in maximizing absorption and effectiveness and preventing any unwelcome side effects.

One of the many reasons we feel so strongly against multivitamins is that they do not consider individual needs (we at Why Not Natural believe one-size-fits-all supplements are one-size-fits-none).

What vitamins and supplements should not be taken together?

Calcium and Magnesium

The relationship between calcium and magnesium is a complex one. Both play critical roles in muscle function, nerve transmission, and bone health.

However, since they compete for absorption in the body, there might be better options than taking them together (Nutrients, 2020). Consider spacing them out throughout the day to maximize absorption if you need to take both.

Calcium and Iron

Similarly, calcium can inhibit the absorption of iron, particularly non-heme iron found in plant-based foods and supplements (American Journal of Clinical Nutrition, 1991). So if you're taking both, it's best to take them at different times.

Vitamin C and B12

The jury's out on this one: some research suggests vitamin C degrades vitamin B12. However, while this phenomenon has been demonstrated in a laboratory, it has yet to be replicated in the human body.

We recommend spacing them out by at least two hours to exercise caution. For example, vitamin B12 is ideally taken first thing in the morning, while vitamin C can be taken throughout the day.

Zinc and Copper

Zinc and copper have an antagonistic relationship in the body. High doses of zinc can interfere with absorption of copper, potentially leading to deficiency (American Journal of Clinical Nutrition, 1998).

Therefore, if you're taking zinc supplements, ensuring adequate copper intake and taking any supplements at different times is essential. You should also note that it's not recommended to take high-dose zinc supplements (some on the market contain 50 mg of zinc, which can wreak havoc on your digestive system in addition to causing a copper deficiency).

Vitamins Not to Take with B12

Vitamin B12 doesn't have many antagonistic interactions with other vitamins or minerals. However, there's some evidence that large doses of Vitamin C, Vitamin E, or potassium supplements might affect the absorption of Vitamin B12 (NHS UK).

So, it may be best to take these at different times.

Vitamins Not to Take with Magnesium

Magnesium can interfere with the absorption of calcium and can also compete with zinc for absorption pathways. Additionally, taking magnesium and bisphosphonates, an osteoporosis medication, can interfere with its effectiveness (National Institutes of Health).

What Vitamins Can I Take Together Daily?

Some many vitamins and minerals can be taken together without any issues. For example, the B vitamins work best in combination, and it's recommended to take a B complex vitamin that contains all eight (like Why Not Natural's B Complex)

Vitamin D and Vitamin K can be taken together as they both assist in bone health, with Vitamin D aiding in calcium absorption and Vitamin K directing calcium to the bones and away from arteries. Why Not Natural's D3-K2 supplements combine them because of their synergistic relationship.

Should You Take Vitamins All at Once or Throughout the Day?

Whether to take all your vitamins at once or spread them throughout the day can depend on a few factors, such as your specific vitamins, your personal schedule, and your body's needs. For example, some vitamins and supplements are best taken with food, while others are better on an empty stomach.

Some vitamins might have stimulating effects and be better suited for morning use, while others, like magnesium, might have a calming effect and be better suited for evening use. Your healthcare provider can provide personalized advice.

Comparison Chart

Vitamin/Supplement Should Not Be Taken With
Calcium Magnesium, Iron
Magnesium Calcium, Zinc
Zinc Copper
Iron Calcium
Vitamin B12 Large doses of Vitamin C, Vitamin E, Potassium
Vitamin C Vitamin B12 (in large doses)
Vitamin E Vitamin B12 (in large doses)


The vitamin and supplement world can be complex, but with some knowledge, you can navigate it effectively to meet your nutritional needs. As always, consult your doctor before starting or adjusting any supplement regimen.

Don't forget to subscribe to our newsletter to learn which supplements to take, how to combine them for maximum benefit, and other health tips to boost your energy and vitality. Plus, discover natural strategies to reduce hormonal imbalances, stress, and anxiety. Click here to get started! 

vitamins and supplements that should not be taken together

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