What Vitamins Should Not Be Taken Together?

BETWEEN THE SUPPLEMENTyour doctor recommended, that probiotics pack you take, your multivitamin, a daily creatine shake, and whatever other supplements on your list—you may start to feel like you need a set of alarms to keep track of all these pills and powders. It makes you wonder: should any vitamins not be taken together?

Certain vitamins and/or supplements shouldn’t be taken in tandem for important safety precautions. As Kim Yawitz, R.D., puts it, most people take vitamins and supplements because they want to be healthier, but taking the wrong ones together can do more harm than good.

“There are many different reasons for this, and it often comes down to how different nutrients are metabolized,” says Yawitz. “In some cases, nutrients compete for receptors that carry them into the blood, so taking them together doesn’t do as much good as taking them separately.”

Here’s which vitamins and supplements to not take at the same time.

What vitamins and supplements should not be taken together?

This list gives you a good starting point on what vitamin and supplement combos to avoid, but there are loads of potential bad combos. It goes without saying, but always consult with your doctor or registered dietitian regarding your personal concerns around vitamins and supplements.

Calcium and Iron

These minerals are not recommended to take together due to calcium’s ability to reduce iron absorption, says Umo Callins, R.D.

“Research shows that calcium can inhibit absorption of heme iron which is the iron found mainly in meat, fish, and poultry as well as non-heme iron, the type of iron found in plants,” says Callins. For someone that is iron deficient, taking the two at separate times to encourage better absorption of iron.

Calcium and Magnesium

Calcium competes with magnesium for intestinal absorption and transport. For this reason, Yawitz recommends taking these supplements several hours apart and only if your doctor tells you to use them.

“Calcium is fortified in many food products and is a part of the formulation in multivitamins and healthy convenient foods such as protein shakes and bars,” Callins says. “If magnesium deficiency is a concern or if intake of magnesium-containing foods is low, it’s important to pay attention to how much calcium is consumed to avoid risk of magnesium deficiency.”

Zinc and Copper

First things first: For most people, there is no need to supplement zinc and copper. If you do have to take zinc per doctors orders, don’t take more than the daily recommendation, which is 8 mg/day for women and 11 mg/day for men. Too much zinc can cause some serious side effects.

“Multiple studies have shown that too much zinc intake from supplements can reduce the absorption of copper and potentially cause copper deficiency,” says Callins. “Both minerals compete for absorption in the body, so taking them together can reduce how well they are absorbed.”

Caffeinated Pre-Workout and Green Tea Extract

Do you chug a caffeinated pre-workout drink or take a pre-workout pill with caffeine and pop a few supplements with green tea extract at the same time?

“If you use a caffeinated pre-workout, you should probably avoid green tea extract (or any supplement with caffeine),” says Yawitz. “Taking too much caffeine can actually decrease exercise performance and may cause anxiety, heart palpitations, jitters, nausea, and other serious health complications.”

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Green Tea and Iron

Callins cautions that green tea extract—a common ingredient in many supplements to help boost energy—can inhibit iron absorption.

“However, strong evidence shows that compounds in green tea and green tea extract (otherwise known as catechins) can interfere with the absorption of non-heme iron, the iron form found in plants,” Callins says. “For individuals who are anemic, or don’t consume enough iron in their diet or take iron supplements, it’s recommended to be aware of this and pay close attention to supplement labels.”

Greens Powder and Iron

Think you’re doing your body and mind good by sipping on a shake infused with greens powder? If you take an iron supplement, too, beware: “All greens powders are different, but if you already take iron supplements, you may want to look for one without iron,” says Yawitz.

In the short-term, taking too much iron can cause nausea, abdominal pain, vomiting, and diarrhea, she says, while overdoing it consistently may leave you susceptible to stomach inflammation and ulcers.

What are symptoms of a bad vitamin and supplement combination?

Some bad vitamin and supplement combinations will reveal themselves immediately with significant symptoms, but sometimes you won’t see any symptoms until there’s a serious problem. “Whenever one supplement decreases the absorption of another, you’d be lucky to see any symptoms before a clinical deficiency sets in,” Yawitz says. These symptoms vary quite a bit by nutrient. Here’s a few.

Symptoms of a Bad Vitamin/Supplement Combination:

• Itchy skin, hives, or rashes
• Gastrointestinal discomfort such as nausea, vomiting, or stool changes
• Fatigue
• Dizziness
• Weakness
• Changes to hair/skin/nails
• Irregular heartbeat
• Changes in urine color and output
• Pain in joints and/or muscles
• Shortness of breath or wheezing
• Weight loss
• Loss of appetite

“If any negative side effects or symptoms are experienced after a new supplement or vitamin combination is consumed, stop the use of the supplement, and reach out to your healthcare provider,” says Callins.

Again, you might not experience any of the negative symptoms from taking an unsafe combination of vitamins and/or supplements, so that’s why it’s always important to take vitamins and supplements only under the guidance of a certified healthcare professional.

How to Mix Vitamins and Supplements Safely

The short answer: Always talk to your doctor or a trusted healthcare practitioner regarding any vitamin/supplement combinations you are taking, or vitamin/supplement additions you’re making to your routine in general.

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Beyond that, Yawitz says you can sometimes avoid negative supplement interactions by carefully reading your product labels. “But unfortunately, many of these bad combinations are sneaky,” she says, and if you lack deep knowledge of biochemistry and nutrient metabolism, you might not even know you’re at risk.

Overall, Yawitz stresses that the easiest way to avoid bad combos is to stop taking vitamins and supplements you don’t need.

“There’s no benefit to taking specific vitamins and minerals if you don’t have a true deficiency, and many of the health supplements out there haven’t been studied enough to know if they’re safe or even effective,” she says. “You can take a high-quality multivitamin if you think you might be falling short in certain nutrients, but you should really visit your doctor for blood tests before adding any individual vitamins or minerals.”

Callins outlines the following plan of action to determine what combination of vitamins and minerals is safe and effective to take together:

• Speak with your doctor or a registered dietitian. We know we’ve said it before, but it bears repeating. Your doctor can provide medical guidance for best practices of when to take the vitamins and supplements and any foods, vitamins, supplements, medications with which you should avoid taking them.
• Read labels thoroughly. Be mindful to read all supplement facts for vitamins, supplements, and food products that may be fortified such as nutritional beverages and bars to ensure you aren’t taking too many combinations of supplements that may be taken together.
• Space out the timing. For supplements and vitamin combinations that may interfere with each other, try taking them at separate times to help with optimal absorption and minimize any undesirable symptoms.
• Less may be more when it comes to supplementation. Taking in excess of what you need may have unintended consequences or result in very expensive urine.

One more note on vitamin and supplement consumption in general: “Because vitamins and minerals are associated with health benefits, it’s easy to assume that more is better (or at least, that more is safe),” says Yawitz. “But many nutrients have safe upper limits, and taking too much can be bad for your health.” Hence, why talking to a doctor or pharmacist before adding vitamins and supplements to your routine is so important.

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