Sleep issues are more common than ever. Trouble falling asleep, waking up in the middle of the night, or just not feeling rested—many of us know the feeling. While there are many reasons for poor sleep, one nutrient is gaining attention for its surprising role: vitamin D.

Most people think of vitamin D as the "bone health" vitamin. But new research shows it also plays a role in brain function, mood, immune health, and yes, sleep.

What Exactly Does Vitamin D Do in the Body?

Your body makes most of vitamin D when sunlight hits your skin. From there, it goes through your liver and kidneys to become active. Once active, vitamin D helps regulate calcium and phosphorus for your bones and muscles. It also helps build a strong immune system, brain health, reduce inflammation, and even improve sleep-related processes.

Vitamin D does all this by binding to vitamin D receptors (VDRs) found in many parts of your body, including your brain.

How Does Vitamin D Help Sleep

Sleep is controlled by a network of hormones, neurotransmitters, and your body’s internal clock. Vitamin D plays a role in all of these:

• Melatonin production: Vitamin D supports the creation of melatonin, the hormone that tells your body when it’s time to sleep.

• Circadian rhythm: It helps regulate "clock genes" like Bmal1 and Per2, which influence your sleep-wake cycle.

• Mood and neurotransmitters: It affects serotonin and dopamine levels. Low levels of these can lead to poor mood and disrupted sleep.

• Inflammation: Vitamin D helps lower inflammation, which is often linked to sleep apnea, restless leg syndrome, and poor sleep quality.

• Muscle health: Deficiency may lead to muscle pain or restless legs, which can keep you up at night.

This mix of effects makes vitamin D a major player in how well you sleep.

The Problem: Vitamin D Deficiency Is More Common Than You Think

If you live in a place with long winters, have darker skin, or spend most of your time indoors, you could be low in vitamin D—even without knowing it.

In the U.S., about 1 in 5 people have a moderate deficiency, and 2.6% of those have a severe deficiency. In parts of Europe, up to 60% of people have low vitamin D.

Since symptoms are subtle, it often goes unnoticed. But even a mild deficiency in vitamin D can interfere with how well you sleep.

Vitamin D Deficiency Symptoms

• Feeling tired even after 7 to 8 hours of sleep

• Muscle aches or weakness

• Feeling down or irritable

• Trouble staying asleep

• Restless legs at night

• Getting sick more often than usual

These can all impact your sleep, so it's worth checking your vitamin D levels if you notice any of them. Mito Health can help you test for vitamin D and other sleep-related biomarkers with their comprehensive and advanced blood testing.

Does Supplementing Vitamin D Improve Sleep?

Yes, but mostly if you're low on it. Many studies show that people with vitamin D deficiency who take supplements see real sleep improvements. They experience better sleep quality, falling asleep faster, and staying asleep longer.

For example, a study found that people with sleep issues who took high-dose vitamin D for eight weeks slept better and fell asleep faster. In pregnant women and older adults (groups at risk for deficiency), supplements also helped with sleep and mood.

But if your levels are already normal, extra vitamin D won’t make you sleep better. Some studies even showed no change in sleep. That’s why blood testing for vitamin D and other nutrients is important before starting on any supplement.

Ways to Optimize Your Vitamin D Levels for Better Sleep

1. Get under the sun: Spend 10 to 30 minutes in direct sunlight a few times per week. The time needed depends on your skin tone, location, and season.

2. Food sources: Eat more food rich in vitamin D, like fatty fish, eggs, fortified or plant-based milk, and fortified orange juice.

3. Vitamin D supplementation for sleep: If your vitamin D levels are low, your doctor may suggest you take a supplement. However, don’t self-dose because too much can be harmful to your body. Safe daily doses vary, but 600 to 800 IU is the general recommendation for adults, while some may need more under supervision.

For best absorption, take it with a meal that contains fat.

One Piece of the Sleep Puzzle

Vitamin D supports better sleep, especially if your levels are low. But sleep is complex, and there are other habits that matter just as much. Getting consistent, quality sleep also means:

• Going to bed and waking up at the same time every day

• Spending time in natural daylight and dimming lights at night

• Eating a nutrient-rich, balanced diet

• Staying active during the day

• Reducing screen time before bed

Think of vitamin D as one of your body's sleep helpers—and a critical one if you’re deficient. To know for sure, get tested. With Mito Health, you can track your vitamin D levels and other key biomarkers that affect how you sleep, recover, and age.

Related Articles

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• The Critical Importance of Vitamin D for Working Adults

• How to Reduce Chronic Inflammation Naturally: Vitamins, Nutrition, & Lifestyle Changes

• How Sleep Patterns Change as You Age and What You Can Do

• Struggling with Deep Sleep? Here's What You Might Be Missing

Resources:

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC5529228

2. https://www.mdpi.com/2072-6643/17/5/803

3. https://pubmed.ncbi.nlm.nih.gov/30275418

4. https://www.researchgate.net/publication/360655452_The_effect_of_vitamin_D_on_sleep_quality_A_systematic_review_and_meta-analysis

5. https://doi.org/10.1152/ajpregu.00168.2024

6. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1595813/full