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Can Vitamin Supplements Cause Insomnia? (Research Review)

by Dale Cudmore | Updated: May 20, 2023

It’s extremely hard to get too much of any vitamin or mineral from food alone. But when you introduce supplements, it’s possible to get too much and experience side effects.

There isn’t a ton of research on if vitamins can cause insomnia in healthy people because most research focuses on fixing sleep issues.

However, there is some that we can look at, and we’ll be summarizing that research in this short post.

Do Individual Vitamins Cause Insomnia?

Let’s start with individual vitamin supplements (i.e. just one vitamin in a capsule).

In general, it’s pretty tough to get too much of a water-soluble vitamin like vitamin C. If you do consume more than you need, your body can flush it out pretty easily unless it’s an ungodly amount.

So that leaves fat soluble vitamins like A, D, E, and K to investigate.

There is no research at all that I could find that looked at the effects of vitamin A or K on sleep quality, and sleep issues are not known side effects of either or them. Side effects of vitamin A or K toxicity include symptoms like nausea or headaches, which could indirectly cause sleep issues, but those should be obvious (1).

For the other two:

  • Vitamin D - There are mixed results on whether or not vitamin D can cause insomnia. Since a vitamin D deficiency is so common, most studies have found that vitamin D deficiency can cause insomnia and getting more is good for sleep (2,3). However, there is some evidence that too much vitamin D can cause insomnia in certain groups of people (like postmenopausal women).
  • Vitamin E - There is next to no research on vitamin E and sleep. One study I found shows that a combination of melatonin and vitamin E was able to improve sleep quality, but there’s nothing to suggest an adverse effect (4).

SummaryResearch on specific vitamins affecting insomnia is lacking. However, most research does suggest that in normal amounts, single vitamins have a minimal or positive effect on sleep quality.

What About Mineral Supplements?

Minerals like iron, zinc, and magnesium all play a big role in sleep.

A deficiency in any of those can cause insomnia.

However, getting too much of most minerals will cause side effects, but these typically don’t include sleep issues directly.

For example, getting too much zinc can lead to zinc toxicity, which includes symptoms like (5):

  1. Nausea
  2. Vomiting
  3. Loss of appetite
  4. Abdominal cramps
  5. Diarrhea
  6. Headaches

Obviously a bad headache or nausea could cause sleep trouble, but it would be pretty clear what the root cause was.

SummaryInsomnia isn’t a known side effect of consuming most common mineral supplements.

Do Multivitamins Affect Sleep Quality?

Multivitamins are different because they give you more nutrients than you need of more than one vitamin or mineral. This could potentially lead to complex side effects.

In a questionnaire of 772 people, researchers found that (6):

Use of a multivitamin or multiple single vitamins was associated with poorer sleep maintenance compared to individuals who did not take vitamin supplements. There was a tendency for vitamin users to have a greater number of awakenings during the night, more total wake time during the night, greater use of sleep medications, and a higher rate of insomnia than non-users.

There are of course limitations to what you can draw from a questionnaire, as these are simply correlations.

As the researchers noted, this result could be explained by poorer sleepers being more likely to try vitamins.

Still, it’s enough to want to explore this topic further.

An interventional study treated adults with insomnia with a broad-spectrum micronutrient formula (similar to a multivitamin) (7). They found significant improvements in insomnia symptoms, mood, stress, and anxiety.

Unfortunately, there’s not any more robust data on this topic at the moment.

SummarySome research suggests that multivitamins could cause insomnia in the general population (mostly healthy people with already good sleep), while other research shows that multivitamins can improve sleep in those with existing sleep problems.

It’s Possible Some Multivitamins Are Better Than Others

Another factor to consider is that all supplements are different and may have different effects.

It’s possible that some combinations of vitamins and minerals are good for sleep quality, while others are bad.

For example, one study had subjects take a vitamin B, magnesium, and melatonin supplement and found that it (8):

...has a positive effect on sleep regulation and can be used to treat insomnia.

It’s going to take a very long time for researchers to figure out all those complex relationships.

Other Explanations of Why a Supplement Could Cause Insomnia Symptoms

If someone starts taking a vitamin and suddenly starts to experience insomnia symptoms, there’s a chance that it’s not the vitamin itself.

There are 3 other plausible explanations:

  • Supplement quality - Many supplements are not pure and don’t contain exactly what’s on the label. Research has shown that some even contain different ingredients that could be the actual ones causing sleep issues (9).
  • The form of supplement - Most mineral supplements can be made in different forms. For example, magnesium supplements come in many forms like magnesium-citrate and magnesium-glycinate. There are known reactions to some of these other ingredients like citrate or glycinate in this example.
  • Other changes in life - Sometimes we attribute negative things to the wrong causes. If sleep issues suddenly started about the time someone starts taking a vitamin, it’s possible that other changes in their life that are causing stress could be the real cause of insomnia.

SummaryIf a particular vitamin is suspected of causing sleep issues, switching to a different brand or form could be one thing to test.

Summary: Do Vitamins Cause Insomnia?

Ideally everyone should just eat healthy to sleep well, but real life isn't always ideal and some situations might make someone want to take vitamins.

There’s a bit of research showing that multivitamins may cause insomnia in healthy people without sleep issues.

However, it’s far from conclusive and just about all other research on vitamin supplements and sleep quality show that they have either no effect or a slight positive one.

So while it’s not a definite answer, it appears that vitamins are unlikely to cause insomnia unless perhaps someone is consuming a ridiculous amount of them. 

If someone is having insomnia symptoms they should see a doctor anyways, who can then run tests to figure out if the cause is a vitamin or something else.


  1. NIH: Vitamin A
  2. Depressed adolescents in a case-series were low in vitamin D and depression was ameliorated by vitamin D supplementation
  3. The effect of vitamin D supplement on the score and quality of sleep in 20–50 year-old people with sleep disorders compared with control group
  4. Effect of Melatonin and Vitamin E on EEG, Sleep Quality and Quality of Life of Shift-Working Nurses in Arak Hospitals
  5. NIH: Zinc Fact Sheet
  6. Vitamins and sleep: an exploratory study
  7. Effect of Micronutrients on Insomnia in Adults: A Multiple-Baseline Study
  8. The Effects of Magnesium – Melatonin - Vit B Complex
  9. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.