What Vitamins Should Not Be Taken Together?

If you’ve slowly been adding one bottle at a time to your supplement collection, you might find yourself in a familiar routine: You sit down with your morning coffee and a handful of pills—calcium, iron, magnesium, and vitamin D, and maybe zinc and fish oil, too. And then when you look at all those pills, you may wonder: “What vitamins should not be taken together?”

First, some good news: Most combinations are safe. The issue with combining certain vitamins is typically not about potential dangers, but about how much of them you’ll absorb. The solution is often to space out your supplements a little more—from each other and from certain foods. Plus, if you take any prescription drugs, such as thyroid medication or hormone therapy, you may need to be extra cautious. 

We’ll explain here why certain vitamins interfere with each other, the pairs you’ll want to separate, and the pairs that work best together—plus, we’ll share a sample daily schedule to help you come up with a plan.

And remember, you can always talk with a healthcare professional—including a Midi clinician—for more individualized guidance on your specific supplements and medications, which vitamins should not be taken together, and any other health issues you’re thinking about.

Why Do Some Vitamins and Minerals Compete With Each Other?

When you take a vitamin or mineral supplement, your body absorbs those compounds into your bloodstream through your gut. Some vitamins and minerals use the same absorption pathways. And if you take high doses of two or more minerals that use the same pathways, one may get “crowded out,” so you don’t absorb as much of it. So, the answer to “What supplements should not be taken together?” is often the ones that your body absorbs in the same way.

Still, this usually only happens when you take high doses of single-vitamin or single-mineral supplements, such as calcium and iron or vitamin C and vitamin B12. In a multivitamin, the amounts of different vitamins and minerals don’t usually compete with each other. Midi clinicians typically recommend you get as much of your recommended vitamins and minerals as possible from food first, then supplement as needed if you have a deficiency or another condition that warrants it.

How much of a supplement you absorb can also change based on what you eat. Fat-soluble vitamins—vitamins A, D, E, and K—are absorbed best when you take them (or eat foods containing them!) alongside some dietary fat. Water-soluble vitamins—vitamins B and C—don’t need help from specific foods to enter your bloodstream.

Calcium and Iron: The Pairing That’s Often Misunderstood

Which supplements should not be taken together? Here’s a classic example, especially for women ages 40 and up: calcium and iron.

Your clinician might have recommended calcium supplements to protect your bones as your natural estrogen production fluctuates and declines ahead of menopause. They might also have recommended iron supplements if you’re low in this nutrient due to heavy periods. But can you take iron and calcium together?

No, and here’s why. Calcium, especially in high doses, can block iron from being absorbed in your intestines. Clinicians typically recommend that you don’t take these two supplements together. They may also suggest that you avoid eating calcium-rich foods like dairy products, tofu, and broccoli at the same time you take an iron pill.

The fix is pretty straightforward: Separate your iron and calcium supplements (or iron supplements and calcium-rich foods) by 2 hours.

It’s also a good idea to take iron on an empty stomach along with some vitamin C, like a glass of citrus juice, which may help your body absorb the iron.

Can You Take Calcium and Magnesium Together?

They’re often sold together in one product, so yes, you can take calcium and magnesium together, in moderate doses.

When doses get high, these compounds might compete for absorption. That’s why some clinicians—including those at Midi—recommend spacing them out.

Here’s what Midi clinicians typically suggest: 

• Take calcium with meals in divided doses of 500 milligrams (mg) or fewer.
• Take magnesium 30 to 60 minutes before bedtime.

Your specific dosing will depend on your clinician’s recommendations, of course. They might also suggest you take vitamin D, which supports absorption of both calcium and magnesium. 

Iron With Coffee and Tea: Timing Matters More Than the Pill

Coffee and tea contain natural plant compounds called polyphenols, including tannins. These compounds bind to iron molecules in your digestive tract, interfering with iron absorption if you take a supplement too close to when you’re sipping your cuppa joe. 

To make sure you’re maximizing your iron supplement, avoid coffee and tea for 2 hours before or after taking your pill. (And remember: You also should avoid taking iron with dairy products or other high-calcium foods.)

Some people feel a little nauseated or constipated when they take iron supplements. Your clinician might recommend you take this supplement every other day instead of every day to cut down on these side effects.

Zinc, Copper, and Iron: The Mineral Trio to Keep Apart

A healthcare professional might recommend that you take zinc supplements to manage hormone levels, reduce hair loss, or even support your immune system. But taking zinc mainly helps when you’re actually deficient in it (and even then, the evidence is mixed). And taken in high doses of more than 15 to 30 mg per day, zinc can compete with copper and iron for absorption, potentially even causing too-low levels of these minerals over time. 

You shouldn’t take a stand-alone zinc supplement indefinitely, unless your clinician advises you to. A less-risky move than taking long-term, high-dose zinc supplements? Prioritize foods high in this mineral or take a balanced daily multivitamin.

Adult women typically need only 8 mg of zinc per day (11 mg when pregnant). There’s about 3 mg in your average bowl of fortified breakfast cereal, for reference. 

Vitamin D and K2: A Pair That Belongs Together

It’s not only about which vitamins should not be taken together. Sometimes there are vitamins you should take at the same time. A prime example is vitamin D3 and K2.

Here’s why: Vitamin D3 helps your body absorb calcium into your blood. Vitamin K2 activates a specific protein that helps your body absorb that available calcium directly into your bones to support bone density. It also activates a protein that may prevent calcification in your arteries. A win-win, particularly in midlife, when women lose bone density faster. This combo is so powerful, Midi combines the two in custom formulas like Daily Omega-3+ and Daily GLP-1 Support.

Vitamins D and K are both fat-soluble, so you can get even more bang for your buck by taking these together, along with foods containing some heart-healthy fat, like avocado, olive oil, or salmon.

There is one thing to be cautious about: Vitamin K can interfere with the blood-thinning medication warfarin (Coumadin). If you’re taking warfarin, always talk with a clinician before starting any new supplements. Vitamin K doesn’t interfere with other blood thinners, but it’s still always a good idea to check with your prescribing clinician before adding any supplements to your routine.

Which Vitamins Can Be Taken Together Safely?

If some of the cautions above spark a little concern, remember: Most vitamins can be safely taken together. The proof is in a standard multivitamin. Those once-per-day pills have lots of different vitamins at appropriate doses that you can take together without concern.

Here are some different combinations you can take together, such as:

• iron and vitamin C to improve iron absorption
• vitamin D3, vitamin K2, and calcium for bone health
• vitamins D3 and K2 plus omega-3 fatty acids, CoQ10, and astaxanthin for joint and heart health (a combo found in Midi’s Daily Omega-3+ supplement)

What Supplements Should Not Be Taken With Hormone Therapy?

What if you’re receiving hormone replacement therapy (HRT, now commonly referred to as menopause hormone therapy, or MHT)? Are there any vitamins you need to be careful about?

This is mainly not a concern: Most vitamins and minerals—including calcium, vitamin D, magnesium, and iron—don’t interfere with estradiol or progesterone. 

In certain cases, the one to watch out for is biotin, a B vitamin. At high doses, it can interfere with a blood test assessing your hormone levels (including thyroid hormone). To avoid inaccurate results, you shouldn’t take biotin supplements for at least 2 days (longer if you take high-dose biotin) before any hormone or thyroid tests.

Some other supplements that aren’t vitamins or minerals, though, require more caution while you’re using hormone therapy:

• St. John’s wort: This speeds up how quickly hormone therapy breaks down, making it less effective at reducing your symptoms.
• Black cohosh, Siberian rhubarb, maca, and soy: These botanical supplements are often used to help manage hot flashes and may be used alongside HRT— but only under the guidance of a clinician. They may interfere with hormone therapy or hormone-sensitive cancers.
• Pregnenolone: This steroid supplement shouldn’t be used alongside HRT without monitoring by a clinician.

The best thing to do is talk openly with your clinician about any supplements you’re taking or are considering taking. This way, they can help you avoid or manage any potential interactions. 

Supplements That Interfere With Thyroid Medication

If you’re taking the thyroid medication levothyroxine, you also need to be careful about certain vitamins and supplements.

Fiber, calcium, iron, and soy supplements, as well as multivitamins, can decrease how much thyroid medication your body absorbs, so you should wait at least 4 hours to take any of these after taking your thyroid meds. You should take levothyroxine on an empty stomach and wait 30 to 60 minutes afterward to eat or drink anything, including your morning coffee. If you take it at bedtime, it should be at least 2 hours after your last meal.

What Vitamins to Take Together Chart: A Sample Daily Schedule

Looking for a simple, streamlined way to remember all of this? Here are a couple sample “what vitamins to take together” charts you can reference. These are just examples, not something everyone should follow. You can create your own version and share it with your clinician to help you talk through the best schedule for you.

If you’re taking iron and thyroid medication, consider:

If you’re not taking iron or thyroid medication, consider:

Just remember that this is general information and shouldn't be taken as medical advice. Talk with your healthcare professional for individualized guidance.

When to Ask a Clinician Before Adding a Supplement

It’s always a good idea to check with a clinician before trying a new supplement. That’s especially true if you’re taking any prescription medications already, or if you’re starting a new one, like hormone therapy, thyroid medication, or a blood thinner. 

Talk with a clinician if you’ve received a diagnosis of any specific vitamin or mineral deficiencies, as well as if you’re taking more than three or four supplements every day to avoid potential interactions. 

When needed—especially for thyroid levels, iron, and sometimes vitamins D and B12— your clinician can order blood tests that help determine whether supplements or medications are needed. They can also offer guidance on the best time to take certain supplements and how much you should be taking. 

Remember, even though vitamins are available over the counter and seem “natural,” it’s still possible to take too much. Taking multiple supplements without being extra careful about their ingredients could easily tip you over the edge without realizing. Remember: Getting as many nutrients via healthy eating as possible is always an excellent bet.

And keep in mind: A Midi clinician can answer any of your questions about supplements as part of a midlife visit about your overall health. Their expertise can help bring you the symptom relief and head-to-toe wellness you’re looking for.

Key Takeaways

• What vitamins should not be taken together? Typically, high doses of vitamins that are absorbed via the same pathways in your gut shouldn’t be taken at the same time, because one can “crowd out” the other, meaning you absorb less of it.
• Calcium and iron are best not taken together, and same with vitamins C and B12. Vitamins D3 and K2 are examples of vitamins that are best taken together.
• If you’re taking the blood-thinner warfarin, hormone therapy, thyroid medication, or other prescription medications, it’s smart to speak with a clinician before starting any new vitamins or supplements in case they could interact with your medications.
• Talk with your clinician about which vitamins and supplements they recommend and the best times of day for you to take them, so you can get the most out of them.

Frequently Asked Questions (FAQs)

Can I take 5 different vitamins at once?

It depends on what those vitamins are. It may be more effective and safer to take them in the form of a multivitamin, which is formulated with safe doses of many different vitamins.

What vitamins interact with vitamin D?

Vitamin D does not typically interfere with other recommended doses of vitamins or minerals.

What vitamins can I take together daily?

You can take many vitamins together daily, as evidenced by multivitamins that contain many vitamins in one pill. Some examples are vitamins D, K2, and calcium. Talk to your clinician about the supplements and vitamins you’re taking, to get the most ideal schedule.

What vitamins aren’t recommended to be taken daily?

Some clinicians recommend taking iron every other day instead of daily to limit side effects. Other vitamins can be taken daily in appropriate doses. It’s possible to take too much vitamin A, C, E, and calcium, for example, if you’re taking high doses every day.

What vitamins are best avoided at night?

Vitamin B12 may feel energizing, so you might not want to take it at night. And high doses of vitamin D may affect your sleep quality.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professoinal with any questions regarding a medical condition or before starting any new treatment.