Low vitamin D levels are directly associated with hair loss across multiple clinical studies, with deficient individuals showing significantly higher rates of telogen effluvium and alopecia areata compared to those with adequate levels. Correcting a deficiency typically leads to regrowth within 3 to 6 months.
This article is for informational purposes only and does not constitute medical advice. Get blood work before supplementing vitamin D.
The Role of Vitamin D in Hair Growth
Vitamin D is not just a vitamin. It functions as a hormone that binds to receptors throughout the body, including vitamin D receptors (VDRs) on hair follicle cells. These receptors play a critical role in the hair follicle cycle, specifically in initiating the anagen (growth) phase.
When vitamin D levels drop below optimal, follicles have difficulty transitioning from the resting phase (telogen) to the growth phase (anagen). The result is increased shedding, slower regrowth, and thinner hair over time.
How Vitamin D Affects the Hair Cycle
| Hair Cycle Phase | Role of Vitamin D | Effect of Deficiency |
|---|---|---|
| Anagen (growth) | Stimulates follicle stem cells to begin new growth cycle | Delayed or failed initiation of growth |
| Catagen (regression) | Normal transition signal | No significant impact |
| Telogen (resting) | Promotes transition back to anagen | Follicles remain stuck in resting phase |
What the Research Shows
Key Study Findings
| Study | Finding |
|---|---|
| 2013 meta-analysis, Skin Pharmacology and Physiology | Patients with alopecia areata had significantly lower vitamin D levels (mean 11.8 ng/mL) vs healthy controls (mean 20.5 ng/mL) |
| 2017 Indian Journal of Dermatology | 71% of telogen effluvium patients were vitamin D deficient (<20 ng/mL) compared to 48% of controls |
| 2018 International Journal of Trichology | Female pattern hair loss patients had mean vitamin D of 17.3 ng/mL vs 30.2 ng/mL in age-matched controls |
| 2020 Dermatology and Therapy review | Concluded vitamin D supplementation should be considered in all patients presenting with hair loss complaints |
The pattern is consistent across studies: people experiencing hair loss tend to have lower vitamin D levels. This does not prove that low vitamin D causes hair loss in every case, but the correlation is strong enough that testing and correction is standard practice among dermatologists.
Testing Your Vitamin D Level
Vitamin D Level Ranges
| Serum 25(OH)D Level | Classification | Hair Impact |
|---|---|---|
| Below 12 ng/mL | Severely deficient | High risk of hair shedding, often multiple nutrient deficiencies present |
| 12 to 20 ng/mL | Deficient | Associated with telogen effluvium and poor hair quality |
| 20 to 30 ng/mL | Insufficient | Suboptimal for hair cycling, correction recommended |
| 30 to 50 ng/mL | Optimal | Target range for hair health |
| 50 to 100 ng/mL | Adequate (upper range) | No additional hair benefit above 50 |
| Above 100 ng/mL | Potentially toxic | Risk of hypercalcemia, do not exceed |
The test you need is a "25-hydroxyvitamin D" blood test (also called 25(OH)D). This is the standard measurement of vitamin D status. It can be ordered by any physician and costs $20 to $50 out of pocket if not covered by insurance.
Who Is Most at Risk for Deficiency
| Risk Factor | Why |
|---|---|
| Dark skin | Melanin reduces UV-driven vitamin D synthesis |
| Limited sun exposure | Office workers, northern latitudes, winter months |
| Obesity (BMI >30) | Vitamin D sequestered in fat tissue |
| Age over 65 | Reduced skin synthesis capacity |
| Vegan or vegetarian diet | Few plant-based vitamin D sources |
| Malabsorption conditions | Celiac, Crohn's, gastric bypass |
How to Correct Vitamin D Deficiency
Supplementation Protocol
| Current Level | Loading Dose | Duration | Maintenance Dose |
|---|---|---|---|
| Below 12 ng/mL | 5,000 to 10,000 IU/day vitamin D3 | 8 to 12 weeks | 2,000 to 4,000 IU/day |
| 12 to 20 ng/mL | 4,000 to 5,000 IU/day vitamin D3 | 8 weeks | 1,000 to 2,000 IU/day |
| 20 to 30 ng/mL | 2,000 to 3,000 IU/day vitamin D3 | 8 weeks | 1,000 IU/day |
Always take vitamin D3 (cholecalciferol), not D2 (ergocalciferol). D3 is more effective at raising and maintaining serum levels. Take it with a meal containing fat for better absorption.
Retest Schedule
Recheck your 25(OH)D level 8 to 12 weeks after starting supplementation. Adjust the dose based on results. Once in the optimal range (30 to 50 ng/mL), switch to a maintenance dose and retest annually.
Vitamin D and Other Hair Loss Types
Correcting vitamin D deficiency is important, but it will not reverse all types of hair loss. Androgenetic alopecia (male and female pattern baldness) is driven primarily by DHT and genetics. Vitamin D optimization supports follicle health but does not override hormonal hair loss. Use our Norwood scale guide to determine if your pattern suggests androgenetic alopecia.
If you have both vitamin D deficiency and patterned hair loss, addressing both issues simultaneously gives the best outcome. Correct the deficiency with supplementation and treat the hormonal component with the appropriate medication.
Vitamin D deficiency often co-occurs with iron deficiency, especially in women. Read our iron deficiency and hair loss guide for the complete picture.
Next Step
Upload a photo at myhairline.ai/analyze to assess whether your hair loss pattern is diffuse (potentially nutritional) or patterned (likely androgenetic), and get a personalized recommendation.