Is Vitamin D Deficiency Linked to Insomnia?

Health Line

08-05-2025

Vitamin D deficiency has been linked to a higher risk of sleep disorders like insomnia. The exact reasons for this are unclear. Although research is mixed, taking vitamin D may boost sleep quality.
Vitamin D is a fat-soluble vitamin that's important for your overall health. This nutrient is involved in maintaining the health of your bones, muscles, and immune system.
Despite its importance, many people don't have enough vitamin D. A 2022 study estimated that 22% of people in the United States have a moderate deficiency in vitamin D while 2.6% have a severe deficiency.
A vitamin D deficiency can have several notable effects on your health. One of these is insomnia.
What's the link between vitamin D and insomnia?
Insomnia is a sleep disorder where you have difficulty falling asleep or staying asleep. It's also associated with poor quality sleep, meaning you feel unrested and sleepy during the day, even if you do manage to get some sleep.
Researchers have observed an association between vitamin D deficiency and sleep disorders.
For example, a 2018 review of nine studies linked vitamin D deficiency to a higher risk of sleep disorders. It also associated vitamin D deficiency with poor sleep quality, shorter sleep duration, and increased sleepiness during the day.
How exactly vitamin D deficiency contributes to insomnia isn't known.
A 2020 review notes that receptors for vitamin D are found in areas of the brain associated with sleep. Although more research is needed, it seems that low levels of vitamin D impact how the body regulates sleep.
For example, vitamin D is involved in pathways used to make melatonin, a hormone important for the sleep-wake cycle. It may also help regulate genes that code for other proteins that are involved in controlling sleep.
What are the symptoms of low vitamin D?
Most people with vitamin D deficiency are asymptomatic, which means they don't have any noticeable symptoms.
When symptoms are present, they may include things like:
fatigue
muscle pain
muscle weakness
bone and joint pain
mood changes, such as feeling depressed
Long-term vitamin D deficiency can have negative effects on bone health, leading to rickets in children and osteomalacia in teens and adults.
Can taking vitamin D help insomnia?
If you've been experiencing insomnia lately, you may be wondering if taking a vitamin D supplement will help you get a better night's sleep. Overall, the research into this is mixed.
A 2018 clinical trial involving 89 participants with sleep disorders found that taking a 50,000 IU supplement every 2 weeks for 8 weeks improved sleep quality, reduced the time it took to fall asleep, and boosted sleep duration.
However, a 2021 clinical trial involving 189 participants with vitamin D deficiency found that taking a 20,000 IU supplement of vitamin D weekly for 4 months showed no improvement in sleep duration, daytime sleepiness, or insomnia.
A 2022 review of studies reported that vitamin D supplementation may boost sleep quality. However, the authors noted that this finding should be interpreted with caution due to the limited research into this topic.
They also mention that they couldn't find enough data looking at the effects of vitamin D supplements on specific sleep disorders.
»MORE: Vitamin D benefits.
Can taking vitamin D cause insomnia?
It may seem counterintuitive, but taking too much vitamin D may also lead to sleep troubles. This goes back to the link between vitamin D and melatonin.
Melatonin is a hormone that promotes sleep and its production increases as it gets dark out. Meanwhile, vitamin D can be made during exposure to sunlight.
A 2023 review notes that there's a negative correlation between the two. This means that as vitamin D increases, melatonin may decrease.
In fact, an older study involving 40 people with multiple sclerosis (MS) found just this. Daily supplementation with a high dose (4,370 IU) of vitamin D decreased nighttime levels of melatonin. Meanwhile, a lower daily dose (800 IU) did not affect melatonin levels.
So it's possible that taking too much vitamin D may lead to trouble sleeping.
That's why it's important to chat with a healthcare professional before starting a new supplement. They can recommend how much to take and also make you aware of any potential side effects.
»MORE: Vitamin D dosage.
Takeaway
Researchers have linked vitamin D deficiency to an increased risk of sleep disorders like insomnia. The exact reason for this isn't known, but it appears to be linked to vitamin D's role in pathways associated with sleep.
While it's possible that vitamin D supplementation may improve sleep quality, research into this topic has been mixed. Additionally, taking too much vitamin D may have the opposite effect and actually interfere with sleep.
If you're worried that a vitamin D deficiency may be contributing to your sleep troubles, visit a healthcare professional to discuss your concerns. A simple blood test can be used to confirm or rule out a deficiency.