Why Do Multivitamins Make Me Nauseous?

Multivitamin supplements are a great option even for people with a healthy and balanced diet. They provide concentrated doses of important nutrients and can boost vitamin D, vitamin C, and Omega-3 fatty acids. However, some people experience nausea when taking multivitamins, which can make it harder for them to meet their daily vitamin needs.

But why do people sometimes feel sick after taking a healthy multivitamin? There are many causes and, thankfully, things you can do to avoid it. For example, the best multivitamin tablets often have warnings on the label that may help you avoid getting sick. That said, it’s also worth knowing more about this topic in-depth to ensure you understand it fully.

This article will examine what makes a person feel sick when taking multivitamin supplements, the severity of this problem, whether you should stop taking your healthy multivitamin, and much more. We’ll also discuss replacements for your multivitamin tablets that may help reduce your nausea and ensure you get the nutrients you need.

Common Causes of Multivitamin-Induced Nausea

When taking multivitamin supplements, nausea might come and go and become very intense or light, depending on your reaction. This upset stomach shouldn’t last more than 30-60 minutes, though it could last longer depending on how your body reacts. As a result, it’s important to know exactly what causes your sickness to ensure you avoid it.

The following three issues are the most common sickness triggers after taking a healthy multivitamin. They’re often inherent to the multivitamin, which might be hard to avoid. That said, others are more connected to your body and the ways it reacts to these nutrients. As a result, it’s critical to take a deep look here to understand what’s happening.

a woman wonders why vitamins make her nauseous

High Dosage

Depending on how many multivitamin tablets you take, your nausea may vary. For example, a high dosage might intensify your reaction because of what Texas Health Resources calls “too much of a good thing.” In other words, your body may not be used to such a high concentration of vitamins or minerals in one dose and could react by feeling sick or upset.

As a result, it’s best to avoid multivitamins that boast excessive vitamin levels (such as 600%). You should only get that heavy of a vitamin influx if you’re deficient in it. For example, many people (a majority of us) are vitamin D deficient, and taking heavy concentrations can help boost your levels without upsetting your stomach.

Specific Ingredients

Interestingly, some studies find that an otherwise healthy multivitamin may cause an upset stomach due to specific ingredients in the multivitamin tablets. For example, calcium is often a troubling supplement, especially for people with already high levels of this nutrient. It can cause constipation, kidney stones, and even odd mental states in many people.

Other nutrients to watch include iron, copper, retinol (vitamin A), sugar, and DI-alpha-tocopherol (vitamin E). Typically, you want to avoid excessive amounts of these nutrients or stay away altogether if you already have high levels. It’s important to talk with your nutritionist or general doctor to get blood tests before changing your diet to include more multivitamins.

Individual Sensitivity

Most people have some kinds of sensitivities, including seafood allergies. However, you might even be sensitive to various types of multivitamin supplements. This may include vitamins within the supplement or even the additives. When you’re sensitive, this might cause nausea or even other reactions, especially if you are allergic and react heavily and dangerously to one.

If you think that you’re sensitive to one or more nutrients in your multivitamins, it’s essential to talk with your doctor and get a sensitivity and allergen test. They’ll expose you to small levels of these items and narrow your sensitivity. As a result, you might be able to buy multivitamin tablets without them to keep yourself happy and avoid nausea-related issues.

Dosage and Timing Considerations

If your multivitamin supplements continually make you feel sick or cause other reactions, it’s best to stop taking them and talk with your doctor. There’s a chance that you might have dosage and timing issues. These problems occur when you don’t take your dosage properly or at the right time. Here’s what to keep in mind about your healthy multivitamins.

a woman takes a multivitamin

Splitting Dosage

Some people can easily split their dosage to minimize their potential nausea risks from multivitamin supplements. That doesn’t necessarily mean you should split pills—though you can, if necessary—but that you can spread out when you take your two multivitamin pills, as most come in a paired dosage. If yours doesn’t, you can instead use a pill cutter.

You can take one dose of your healthy multivitamin early in the day to minimize your nauseous reaction. You can then take the other of your multivitamin tablets after eating dinner or later. This approach minimizes your nausea and can help keep you from feeling sick. Play around with dose sizes to find one that feels right for your stomach’s needs.

Taking With Food

In most cases, it’s best to take your vitamins with food. There are a few reasons for that. First, the unique nature of a multivitamin may upset a sensitive stomach and make it feel sick. Furthermore, some vitamins need fat to absorb. They typically take fat from your body but can also use fat in your stomach from the food you just ate to absorb in your digestive system.

That said, some also suggest taking multivitamins on an empty stomach, so there are variations here. Typically, any multivitamin with B12 absorbs best if you haven’t eaten, while vitamins A and D need fat to absorb. Talk with your doctor about your vitamins and gauge what kinds you’re taking to ensure that you plan your meals safely around your multivitamin.

Time of Day

The best time of day to take your multivitamin supplements may vary depending on many factors. For example, those that require an empty stomach are best taken in the morning, or you might develop nausea. However, others should be taken later with food to avoid nausea. Furthermore, some vitamins might cause unforeseen effects that could impact your reaction.

For example, taking high-dose vitamin D supplements at night may increase your metabolism, boost your energy levels, or even cause nausea. It’s critical to seek advice from your doctor on these supplements. Let them know what vitamins you need, and they can create a regimen that minimizes your upset stomach risks and keeps your diet safe.

Common Multivitamin Ingredients That May Cause Nausea

The interesting thing about multivitamin supplements and nauseous stomachs is that some nutrients typically trigger them. This fact can also vary depending on your current health. As a result, even a healthy multivitamin might cause an upset stomach for you, even if it has never happened before. With that said, these four nutrients are the most common culprits.


Iron is essential to your diet and can support your immune system, prevent anemia, and help rebuild your muscles. However, high-dose supplements with lots of iron could easily trigger nausea. Some might even vomit, develop dark stools, experience stomach cramps, get diarrhea, or even feel constipated. These reactions can be very uncomfortable to some.

As a result, it’s essential to get your iron levels tested before taking a multivitamin with high levels. If you already have enough iron in your diet (through eating red meat or other sources), too much more in your vitamins could be a problem. Instead, it’s best to cut out the iron from your multivitamins entirely or get a much lower dosage based on your needs.

Vitamin B Complex

The complex world of Vitamin B includes many different nutrients that can help improve eyesight, boost energy levels, enhance brain function, boost digestion, and even help with proper nerve function. However, too much of a good thing is just that—high levels of vitamin B complex in your healthy multivitamin could leave you with an upset stomach for hours.

The tricky thing about this is that it’s often hard to identify which nutrient in the complex caused this reaction. Put simply, there are many types of vitamin B, and any one of them could have caused your nausea. It’s best to talk to your doctor and undergo a sensitivity test. They can gauge which element in your multivitamin tablets is triggering your nauseous stomach.


Zinc is one of those supplements you should never take on an empty stomach. High-dosage multivitamins with lots of zinc can irritate your stomach lining, cause excessive stomach acid, and even produce gas and bloating. It’s critical for your overall health but can become a real problem if you take too much and don’t carefully monitor your reactions.

Instead, looking carefully at your multivitamin’s label and gauging the zinc level is important. Is it available at a concentrated level that could trigger stomach pain? Or is it a bit more limited and likely more tolerable? Whatever the situation, you should contact your doctor if your multivitamins repeatedly cause stomach aches to ensure you avoid zinc poisoning.


Are you noticing a theme here? Multivitamin tablets containing various heavy metals typically cause the most nausea. The same is true with magnesium, a very healthy metal that your body needs to support itself. However, taking too much magnesium (usually beyond the suggested dosage) can cause diarrhea, vomiting, and nausea in many people.

Frustratingly, these symptoms can be caused by all of the vitamins on this list, so it can be tricky to gauge the actual trigger. A blood test from your doctor can highlight your nutrient levels and give you an idea of what’s wrong. For example, if they find high magnesium levels, it’s likely that this otherwise healthy and beneficial nutrient is triggering your troubling nauseous reactions.

Tips to Reduce Multivitamin Nausea

If you plan on continuing your current multivitamin regiment but are sick of getting nauseous when you take your dosage, here are a few simple tricks that can help:

  • Stay Hydrated: Drinking a steady supply of water throughout the day (a minimum of eight glasses daily) can reduce your nausea and even help your multivitamins break down better.
  • Gradual Introduction: Slowly introduce a multivitamin into your diet (such as alternating days) to acclimate your body. Some may have to always alternate their days to avoid nausea.
  • Choosing the Right Formulation: It’s important to identify multivitamins that meet your sensitivity levels – your doctor can help you find a balanced formula that reduces nausea.

Sean Byers, MD

Sean Byers, MD

Sean Byers is currently a Resident in the Internal Medicine program at UTMB. He studied at the University of Queensland School of Medicine as well as received his Master’s in Public Health with a focus in epidemiology and biostatistics at the University of Southern California. His background is in biology, computer science, public health, and internal medicine.

Recommended Articles


  1. https://www.livestrong.com/article/223327-why-do-you-feel-nauseous-after-taking-vitamins/
  2. https://vibranthealth.com/blogs/blog/why-your-multivitamin-is-making-your-nauseous-what-you-should-know
  3. https://bestlifeonline.com/worst-multivitamin-ingredients/
  4. https://www.discovermagazine.com/health/do-multivitamins-work-and-how-do-you-know-if-you-need-one
  5. https://www.consumerlab.com/answers/cutting-or-breaking-vitamin-or-supplement-tablets-and-capsules/cutting-breaking-vitamin-tablets/
  6. https://health.clevelandclinic.org/the-best-time-to-take-vitamins
  7. https://www.healthline.com/nutrition/multivitamin-side-effects
  8. https://www.verywellhealth.com/do-iron-supplements-for-anemia-cause-upset-stomach-3522504
  9. https://supplementsalon.com/why-does-zinc-make-me-nauseous/
  10. https://www.healthline.com/nutrition/magnesium-supplements
  11. https://www.medicalnewstoday.com/articles/320877
  12. https://www.everlywell.com/blog/vitamins-supplements/why-take-a-multivitamin/
  13. https://www.livestrong.com/article/13719643-how-to-choose-the-best-multivitamin/