Can Supplementing Too Much Vitamin D Cause Insomnia?

I did it again! I managed to aggravate my insomnia with another supplement. What seemed like a very beneficial and benign vitamin turned out to be a sneaky sleep killer. Worst part? I unknowingly suffered for almost a month until I figured out what the heck is going on with me – my vitamin D dose was too high and it was causing some serious sleep issues. Let me explain.

About six weeks ago I started feeling more down than usual. Figured this was the winter blues again – no sunshine here, cold, wet – nasty business. This was the time to listen to science and start supplementing with Vit D for better mood and sleep. And initially it helped – a gentle pick up in mood, less lethargy, more sense of wellness. Good to go!

Two weeks into it I felt like I was doing so good that I could try and quit melatonin altogether (you can read about my experiment here) but I couldn’t fall asleep and it was getting worse and worse. That sense of tiredness and sleepiness never came at 10pm as usual. The little sleep that I got was very fractured and the dreams were insane: violent, paranoid with deep plots, I mean Hollywood would pay big buks for this stuff.

I waited two weeks to allow my body to adjust but things weren’t getting any better so I started back on melatonin but my sleep didn’t improve a bit! Something was wrong but I didn’t know where to look so I had to do what works best – think what new supplement I recently introduced. There were only two suspects – Vitamin D and K2.

Knowing how beneficial D can be in my climate zone I was very reluctant to point my finger at it so I continued taking it till I finally decided to quit for good and see what happens. Bam… Three nights later this alertness at night started subsiding and my sleep is normalizing.

Even more surprisingly, I recently discovered that I could get the same effect from simply staying out in the sun and generating vitamin D without any supplementation. One early spring sunny day I spent an hour sun bathing and that very same nigh I was hot and sleepless which lasted for at least two more weeks. This is just mind blowing for me.

Why Would a Large Dose of Vitamin D Cause Insomnia?

So how can this be? How can Vitamin D cause insomnia?  When I supplemented I took 5,000 IUs, which is way higher than what I did last year – 2,000 IU daily. Also, this year I took K2 and this alone made for better assimilation. I could have gotten a dose several times higher than before. But even with this dose most ‘healthy” individuals have no issues. Some take 20,000 IUs and do well so why did I react? I found there can be a few mechanisms behind it.

Impaired Melatonin Production

This report from ConsumerLabs claims that high amounts of vitamin D may interfere with the body’s production of melatonin. This seems like the most likely scenario because I tried taking melatonin in much higher doses than usual for me and still experienced onset insomnia and light sleep.

Interestingly, Traditional Chinese Medicine (TCM) refers to Vit D as ‘Qi tonic’, concentrated energy from the sun.  If we’re lacking Qi, our internal organs and overall systems don’t function as they should. However if we add too much Qi to already dis-functioning organs we create more trouble. Additionally, melatonin levels are lower in summer and higher in winter so perhaps taking too much Vit D confuses the body into suppressing melatonin production during the time when it needs more of it.

Low thyroid

Kerri Knox, RN (Functional Medicine Practitioner) believes there is a correlation between low thyroid function and low Vit D levels. She also believes that developing symptoms from taking Vit D can point to magnesium deficiency (high levels of D make blood levels of calcium take off, which leave the magnesium/calcium ratio too low: there is too much calcium compared with magnesium.

Low blood magnesium levels are well known to be associated with insomnia. But what really caught my attention was this statement: “there is an amazing correlation between people who have had their appendix removed and those that have vitamin d deficiency”. I surely had my appendix removed about eight years ago. At the same time, I’ve been supplementing magnesium on daily basis for years now so I highly doubt this is a magnesium issue.

Anyways, as I’ve discovered, thyroid issues make things much more complicated because it increases sensitivity to pretty much anything. You pull, it pulls back, you shove, it shoves back. So while low thyroid can make one crave Vit D, an ill-matched dose can quickly create an imbalance and stress.

Lead toxicity

Lead is a potent neurotoxin and can wreak havoc on one’s nervous system. The way I reacted to chelating agent DMSA makes me suspect I might be lead toxic as well. Some studies show that Vitamin D causes a rise in the concentration of lead in the blood stream and in the bones. My mercury chelating buddies seem to suspect this too and advise against Vitamin D until all heavy metals are cleared.

Sudden repletion – jolt to the system

This new study reveals that a sudden change in blood levels of Vitamin D caused postmenopausal women some serious sleep issues. Prior to supplementing these women had low circulating vitamin D and undergoing weight loss. The study finds no explanation for this and speculates that underlying genetic factors that affect vitamin D metabolism may be involved.


Make no mistake – proper Vitamin D levels can work magic on your sleep, especially during winter or cases of low sun exposure. However, learn from my mistakes: research causes of Vitamin D deficiency and see what applies to you. Should you decide to supplement start low and watch for symptoms. General advice I find online about best ratio is to follow this rule: about 2,000 IU per 100 lbs (45 Kg) of healthy, slim weight. Overweight people will need more because fat absorbs more Vit D.

If you are going to sunbathe then start slow. Allow your body to adjust gradually. For any of us with low thyroid function the name of the game is gentle and easy with everything.

Had a bad reaction to Vitamin D and developed insomnia? This is a very interesting phenomenon so please share your experience in the comments.

21 comments… add one
  • G Jun 2, 2019 Link Reply

    Good info. I’d heard that it was always advisable to take Vitamin D only in the morning as it could cause insomnia if taken later in the day. What time of day were you taking it? And did you find anything natural that actually works to help alleviate insomnia?

    • insomniacnextdoor Apr 4, 2020 Link Reply

      Hi, I was taking it in the morning. It’s a fat soluble vitamin, it stays in the system long time so it doesn’t matter when we take it. When it comes to vit D induced insomnia it is very difficult to mitigate it with herbals or minerals. Still looking for answers on way to reduce vit D levels once it is in the system. 😉

  • Sakib Jul 12, 2020 Link Reply

    Hi, I had been taking 5000 IU vitamin D daily for over a month and suffered terrible insomnia and a few days ago I quit and tried sleeping aid to help overcome the insomnia..I was wondering if u have any advice on how I should proceed as I’ve not gotten good sleep in a very long time.
    Thank you

    • insomniacnextdoor Jul 12, 2020 Link Reply

      Hi Sakib, I would wait to vitamin D wears off in a couple of weeks to establish a baseline and see whether it was the reason for insomnia. Unfortunately, I haven’t found any method to help flush vitamin D out of the system other than staying out of the sun and allow it to wear off. Hang in there.

  • D birdflips (sub to me on YouTube if you want to tap into untapped human potential.) Jul 23, 2020 Link Reply

    I’ve been taking 2,000 IU along with zinc, copper, calcium, and magnesium in the right doses so don’t know why for the past week I’ve not been able to sleep for more than a few hours a night. If you found any new info on this please tell me thanks.

    • insomniacnextdoor Jul 23, 2020 Link Reply

      What’s your thinking behind supplementing with copper? Vitamin D does cause this type of sleep disturbance in some people. I’m one of them.

  • Jaden Nov 2, 2020 Link Reply

    So what would be the best recommendation for a person with hyperthyroidism? Is taking a magnesium supplement with a lower dose of vitamin D safe?

    • insomniacnextdoor Nov 3, 2020 Link Reply

      If you are having a reaction then I would avoid Vitamin D. Have you looked into Traditional Chinese Medicine? They have a few formulas that work just as well as the western hormone prescribed therapies. Here’s a link to an article to get you started.

      • Whitney Feb 1, 2021 Link Reply

        There are some threads mentioning vitamin k as a culprit. I started taking vitamin d with mk-2 shortly before my insomnia hit.

        Threads suggest that the mk-2 draws calcium from the blood (then causing insomnia). This person stopped supplements and started calcium, which seemed to help.

        • insomniacnextdoor Feb 20, 2021 Link Reply

          Hi Whitney, isn’t K vitamin is there to avoid drawing calcium from the bones?

  • Indre Nov 6, 2020 Link Reply

    And I thought I was crazy. Two years I started vitamin D because supposedly I was very low and both times my insomnia got so much worse. Never again. Occasional tanning (even indoors in winter no more than 5 minutes per session with beds that have at least 3% UVB) is so much better than taking supplements. I found there is a facebook group called Secosteroid Hormone D which has some interesting information about why we should never take vitamin D.

    • insomniacnextdoor Nov 8, 2020 Link Reply

      Good point about tanning beds, I was going to try it this winter since traveling to a sunny region is not an option. 😉 Will look into to that FB group, thank you Indre.

  • Indre Nov 8, 2020 Link Reply

    I also found this article useful:

    • insomniacnextdoor Nov 8, 2020 Link Reply

      I wonder if they would find the same correlation in general population too, not just MS.

  • carol Dec 20, 2020 Link Reply

    I recently started on vitamin D per my doctor’s request. I did fine on small amounts but once I tried 5,000 IU daily I began having terrible insomnia and night sweats. I would fall asleep and then wake multiple times throughout the night and be unable to fall back asleep. Regardless of what the doctors say, I felt far better being slightly D deficient and sleeping well. I don’t plan to continue with so much and I am hopeful these symptoms will eventually subside.

    • insomniacnextdoor Jan 3, 2021 Link Reply

      Thank you for sharing this, Carol. This is exactly what happened to me too. There is contradicting science on whether we truly need to supplement with vitamin D.

  • Shari Sutherland Mar 3, 2021 Link Reply

    I have had a similar experience with Vitamin D and insomnia. I started taking 5,000 IU in the morning about a month ago, and have had the worst nights’ sleep ever for the past few nights. I exercise outside for a couple of hours every day, so I think I will rely on that and forget the supplement.

    • insomniacnextdoor Mar 7, 2021 Link Reply

      oh for sure Shari, if you can get natural sun exposure on daily basis nothing will beat that 😉

  • Ian Mar 19, 2021 Link Reply

    I too have experienced insomnia as a result of vitamin D supplementation. I have bipolar in my family and there may be a connection with elevated calcium, or a higher calcium / magnesium ratio. That being said, in the winters I do benefit from lower doses (100-400IU). I tend to take it in a pulsed fashion (i.e. a week or so on, then a week or so off) which works better.

  • DebL May 10, 2021 Link Reply

    Well, this just explains everything. I’ve been blaming my extreme insomnia on menopause and just started thinking this morning after being up most of the night that the only supplement I’ve upped this year is D. All of the articles saying Covid outcomes might be worse in the low vitamin D crowd made me up my 1,000 IU a day to 5,000. A year of not sleeping can’t be good for the ol’ immune system either. I’ve had my appendix removed and also have low thyroid. Thanks so much for your site!

    • insomniacnextdoor May 18, 2021 Link Reply

      This is quite an insight, Deb. This could explain this entire Covid insomnia phenomenon, especially for those who never had Covid in the first place. I too have my appendix removed and low thyroid.

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