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Evidence Based

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Can Vitamin D Deficiency Cause Hair Loss?

Written by Dr. Michael Ruscio, DC on October 28, 2025

Written by Dr. Michael Ruscio, DC on October 28, 2025 — Reviewed by Hilary Watts

• Types of Hair Loss|
• The Vitamin D Connection|
• How Vitamin D Might Help Hair|
• How to Increase Vitamin D|
• Other Ways to Reduce Hair Loss|

Hair loss can take a real emotional toll. It’s easy to feel discouraged when you notice thinning hair or a receding hairline. But here’s the good news: These changes aren’t always just cosmetic. In many cases, they can be your body’s way of signaling that something deeper is out of balance—and that means there’s often something you can do about it.

Although aging, hormones, stress, and inflammation all play a role in hair loss, nutrient status is another key factor that often gets overlooked. In particular, low vitamin D levels have been linked to several types of hair loss in research, including both male and female pattern hair loss and alopecia areata. Optimizing your vitamin D may not be the entire solution, but it’s one piece of the puzzle that can make a real difference.

In this article, I’ll break down what the research says about vitamin D and hair health, how deficiency may contribute to thinning hair, and what steps you can take through diet and lifestyle to support healthy growth naturally.

Types of Hair Loss

There are many common types of hair loss (medically known as alopecia). Understanding which type you’re dealing with can help you make sense of what’s driving it—and whether nutrient deficiencies may be part of the picture. 

The following list includes types of hair loss related to changes within the body (rather than chemotherapy or too much pulling from hairstyles) 1:

• Androgenetic alopecia, also called male- or female-pattern hair loss, is the most common type. In men, hair recedes from the temples; in women, it begins as gradual thinning at the part line, eventually spreading across the scalp.
• Alopecia areata accounts for nearly one in five cases of hair loss and occurs when the immune system mistakenly attacks hair follicles.
• Telogen effluvium (TE) happens when too many hairs enter the “resting” phase at once—often triggered by stress, illness, or hormonal shifts. Fortunately, TE is usually temporary.
• Scarring alopecias occur when inflammation damages the follicles and replaces them with scar tissue, as seen in conditions like lichen planopilaris and folliculitis decalvans.

Although some types of hair loss are more difficult or impossible to reverse, many are influenced by factors you can improve—like inflammation, hormone balance, and nutrient status. Low vitamin D, in particular, may be most relevant to androgenetic alopecia and alopecia areata.

How Vitamin D Connects to Hair Loss

Research suggests that vitamin D may play a role in certain types of hair loss—particularly those with autoimmune or hormonal influences. Let’s look at what studies show.

The Vitamin D–Autoimmunity Link (Alopecia Areata)

From a handful of meta-analyses (high-quality studies of studies), we know that vitamin D levels tend to be lower in people with autoimmune-related hair loss conditions like alopecia areata than in healthy individuals without hair loss. In one of these meta-analyses 2:

• People with alopecia areata were almost 5 times more likely to have vitamin D deficiency—about two-thirds (65.4%) were deficient.

While this doesn’t prove that vitamin D deficiency causes alopecia areata, the correlation is strong enough to suggest that optimizing vitamin D might support healthier immune and hair follicle function.

The Vitamin D–Hormone Connection (Androgenetic Alopecia)

According to a systematic (methodical) review, people with androgenetic alopecia (pattern hair loss) have lower levels of vitamin D than their healthy counterparts, and vitamin D tends to be lowest in those with the most severe hair loss 3.

The study also found a strong association between female- and male-pattern hair loss and micronutrient deficiencies—particularly in vitamin D, selenium, B vitamins, iron, and zinc.  

How Vitamin D Might Help Hair

Vitamin D plays an active role in how your hair grows, and when levels drop too low, that process can be disrupted in several ways. Here’s what researchers have found.

1. When Hair Follicles Don’t Get the “Go” Signal

One theory centers on the vitamin D receptors that are located in hair follicles. Researchers have studied this idea using mice that are genetically modified to lack the vitamin D receptor (VDR).

Normally, hair follicles go through phases of growth, rest, and shedding. But in the mice without VDR, the hair cycle got stuck in the “catagen” phase—a stage where the follicle is supposed to shrink and reset for new growth. Instead, parts of the follicle that should have broken down stayed in place, leading to stalled regeneration and eventual hair loss 4.

In short, vitamin D—and specifically the vitamin D receptor—seems to help hair follicles know when and how to regenerate. Without enough of it, the cycle may get disrupted, which could help explain why low vitamin D levels are often linked to thinning hair or alopecia in humans.

2. Vitamin D Keeps the Immune System in Check

Vitamin D also helps your immune system stay balanced. It supports what’s called immune tolerance, which is your body’s ability to recognize its own cells as safe 5. 

Although researchers don’t know exactly why, Vitamin D has been linked to the development and severity of several autoimmune diseases 6, including alopecia areata 7, lupus, inflammatory bowel disease, and autoimmune thyroid disease 8. 

3. The Overlap Between Hair, Thyroid, and Vitamin D

Vitamin D deficiency, hair loss, and thyroid dysfunction often overlap. Here’s what research shows:

• Around 30% of people with hypothyroidism may experience some degree of hair loss 9.
• Vitamin D deficiency is common in both alopecia areata and hypothyroidism 10 11.  
• Many people with alopecia areata also have thyroid antibodies and signs of poor thyroid health 12.

The common link is autoimmunity—the immune system mistakenly attacking its own tissues, whether that’s the thyroid gland (as in Hashimoto’s hypothyroidism) or the hair follicles (as in alopecia areata).

Although research hasn’t yet proven a direct cause-and-effect relationship, maintaining healthy vitamin D levels may help support immune and thyroid function—and, in turn, healthier hair.

Resolving vitamin D deficiency is one of the steps I recommend as part of an overall self-paced program to tackle hypothyroidism. Optimizing vitamin D has certainly been useful for many of my clients who have hypothyroid symptoms, including thinning hair. And the good news is that increasing vitamin D levels is fairly simple for most people.

Does Vitamin D Help Regrow Hair That’s Already Lost?

Right now, there’s no strong evidence showing that oral vitamin D supplements can reverse most types of existing hair loss—but there are some encouraging early findings.

One small study tested high-dose oral vitamin D3 in women with telogen effluvium (the type of hair shedding often triggered by stress or hormonal changes) 13. After taking 200,000 IU every two weeks for three months, more than 80% of participants showed visible improvement in hair growth. 

Although the study had no placebo group to help confirm whether the vitamin D supplement caused their hair growth, the best results were seen in younger women who didn’t regularly use sunscreen and who consumed milk or milk protein—suggesting that sun exposure and dietary calcium might influence how well vitamin D works.

In another small but interesting clinical trial, researchers compared vitamin D levels in women with female pattern hair loss (FPHL) to healthy controls. They found that women with FPHL had significantly lower vitamin D levels than those without hair loss 14. 

To see if correcting this deficiency could help, 45 women with FPHL were divided into three treatment groups for six months:

Group 1: Topical minoxidil (medicine for hair growth) plus oral vitamin D

Group 2: Topical minoxidil alone

Group 3: Oral vitamin D alone

Here’s what they found:

• The combination group (minoxidil + vitamin D) showed the greatest improvement on the Ludwig scale (a standard measure of hair loss severity).
• Minoxidil alone also helped, but not as much.
• Vitamin D alone didn’t significantly improve hair density or structure on its own.

Overall, these studies tell us that vitamin D likely isn’t a magic bullet, but when combined with a solid topical approach and overall lifestyle support, it may make a measurable difference.

External Support: Light Therapy for Hair Regrowth

Vitamin D works from the inside out, but light-based therapies, also called low-level laser therapy or photobiomodulation, act from the outside in—using specific wavelengths to stimulate the scalp directly.

In one randomized controlled trial, people with androgenetic alopecia who used red and blue light LED caps gained an average of 28.5 more hairs per cm², indicating that light therapy shows meaningful benefits for hair regrowth 15. Another study showed similar results, with individuals with androgenetic alopecia showing increased hair density and thickness after light therapy compared with the placebo (no treatment) group 16. 

Interestingly, the type of light used may influence the effectiveness of photobiomodulation for hair growth. A meta-analysis of 36 studies found that ultraviolet and infrared light seem to benefit those with alopecia areata, while red and infrared light appear to be most effective for androgenetic alopecia 17.

Overall, light therapy may be a safe, noninvasive tool that can fit nicely into a holistic approach to hair restoration—but we still need more long-term, standardized research to define best practices.

How to Increase Vitamin D Levels

1. Test and Optimize Your Levels

Before you start supplementing, it helps to know where your levels stand. A simple blood test is usually quick and inexpensive, and can tell you whether you’re low in vitamin D.

For most people, keeping levels around 30–50 ng/mL supports immune, bone, muscle, and thyroid health 18 and may also support hair growth.     

If your results are low, consider vitamin D3 supplementation—typically between 600 and 4,000 IU per day, unless otherwise directed by your healthcare provider. You can also add foods rich in vitamin D, like egg yolks and fatty fish (salmon, mackerel, sardines) 19. 

2. Get Vitamin D Naturally

Sunlight remains one of the most efficient natural sources of vitamin D, but the ideal amount of sun exposure depends on the individual. Factors like your current vitamin D level, skin tone, where you live, the time of day, cloud cover, and even the season all play a role.

Some studies have estimated how much sunlight different skin types need to maintain adequate vitamin D. People with darker skin (phototype V) may need around 25–40 minutes of midday sun exposure (without sunscreen) on about a third of their skin—such as the hands, face, forearms, and lower legs—between March and September 20. Unfortunately, we don’t yet have clear data for those with the darkest skin (phototype VI). Until better research is available, it’s reasonable for those individuals to follow the phototype V guidelines, check vitamin D levels periodically, and adjust sun exposure as needed.

People with lighter skin (phototypes I–IV) typically need less sun—around 9 minutes daily under similar conditions during spring and summer 21.

Though it isn’t perfect, the UV Index is a pretty good scale to help each of us figure out how much time we should spend in the sun at different times of day to avoid burning. You can find apps that show the UV Index for your location and time of year, like the D-minder app. 

Other Ways to Support Hair Growth

Vitamin D may play an important role in hair health, but it’s just one piece of the puzzle. Low levels of B vitamins, iron, selenium, and zinc have also been linked with hair thinning 3. 

Two ways to support a healthy body and healthy hair are improving your diet and managing stress:

• Eat a gut-healthy, anti-inflammatory diet. Approaches like the Mediterranean diet or Paleo-style diets, which are rich in protein, fish, vegetables, nuts, and seeds, can help balance the immune system and reduce inflammation 22.
• Address stress. Chronic stress may disrupt hormones and stem cell activity tied to hair growth 23. Practices like meditation, gentle exercise, and spending time outdoors or with supportive people can help restore balance to your body and mind.

For nutritional and other promising supports for hair health, read The Best Hair Growth Supplements for Fuller, Stronger Hair.

If your hair loss doesn’t improve after a few months of optimizing these basics, it’s worth checking in with your healthcare provider or a trusted functional medicine practitioner to uncover any underlying causes.

In my experience, the path to healthier hair usually begins with the same foundation that supports a healthier body—balanced nutrition, managed stress, and restored gut and immune function. Small, consistent steps in these areas can make a bigger difference than you might expect.

Vitamin D Is a Factor in Hair Health

Whether your hair loss is related to vitamin D or not, making sure you get enough of this vitamin is vital for many aspects of health, so it’s a no-brainer to keep your levels optimal.

But vitamin D isn’t the only thing to look at if you have hair loss. An anti-inflammatory diet will generally help to provide the nutrients you need to protect against hair loss and keep your immune system healthy, so you’re less likely to develop inflammation-related alopecia.

You can get more help with concerns about hair thinning, gut health, or other health issues by reaching out to us at the Ruscio Institute of Functional Health.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.