Biotin or Vitamin D: What is Better for Hair Growth?

October 23, 2025 •

4 min read

According to a study published in the International Journal of Trichology, hair loss patients often exhibit deficiencies in key nutrients like biotin and vitamin D. While both are vital for hair health, the question of what is better for hair growth, biotin or vitamin D, depends on the specific deficiency and underlying cause of hair loss.

Quick Summary

This guide provides a detailed comparison of biotin and vitamin D for hair growth, explaining their different functions, the signs of deficiency, and when supplementation may be effective. It highlights how a deficiency in either can lead to hair issues and emphasizes the importance of a proper diagnosis.

Key Points

Specific Role: Biotin supports the structural protein keratin, while Vitamin D regulates hair follicle cycling, making their roles distinct but complementary.
Deficiency-Dependent Effectiveness: Biotin supplements are most effective for those with a rare, documented deficiency, while vitamin D supplementation can address its more common deficiency linked to hair thinning.
Diagnostic Testing is Key: Relying on guesswork is ineffective. Consulting a doctor for a blood test is the best way to determine if a biotin or vitamin D deficiency is causing hair loss.
Holistic Strategy: For optimal hair health, combining a balanced diet rich in both nutrients, alongside proper medical guidance, often yields the best results.
Patience is a Virtue: Any noticeable improvements from correcting a deficiency with supplements will likely take several months (3-6) to become apparent.

Biotin vs. Vitamin D: Understanding the Fundamentals

Understanding the distinct roles that biotin and vitamin D play in the body is the first step to determining which one might be more beneficial for your hair growth goals. They are not interchangeable and address different aspects of hair health, from the cellular level to the structural integrity of the hair shaft.

The Role of Biotin (Vitamin B7) in Hair Growth

Biotin, a water-soluble B-vitamin, is primarily known for its involvement in metabolic processes that convert food into energy. For hair, its main function is to support the production of keratin, the essential protein that makes up the hair, skin, and nails.

Keratin Production: Biotin is a crucial cofactor for the enzymes involved in creating keratin, directly contributing to the structural foundation of your hair strands.
Strengthening Hair: By aiding in keratin production, biotin can help improve hair elasticity, reduce brittleness, and prevent breakage, which can lead to the appearance of thicker, fuller hair over time.
Targeting Deficiency: Biotin supplementation is most effective for individuals with a documented biotin deficiency, a rare condition that can cause hair thinning and loss. For those with normal biotin levels, supplementation may provide little to no benefit for hair growth.

The Role of Vitamin D in Hair Growth

Often called the 'sunshine vitamin,' Vitamin D is a fat-soluble vitamin with significant influence on the body's hair growth cycle. Unlike biotin, it works more on a regulatory level, affecting the hair follicles themselves.

Hair Follicle Regulation: Hair follicles contain vitamin D receptors, and the vitamin plays a key role in stimulating the creation of new follicles and regulating the normal hair growth cycle.
Addressing Deficiency: Low levels of vitamin D are more common than biotin deficiency and have been linked to hair thinning and certain types of alopecia, including androgenetic alopecia and alopecia areata. Correcting a deficiency can be crucial for reversing hair loss.
Immune System Modulation: Vitamin D helps regulate the immune system, and some research suggests this can help fend off potential scalp issues that might hinder hair growth.

When to Choose Biotin vs. Vitamin D

For most people, the decision isn't about choosing one over the other but understanding which nutrient deficiency is most likely contributing to their hair loss. The best approach often involves a blood test to identify any specific deficiencies.

Here are some key considerations:

If you have brittle hair and nails, biotin deficiency might be a factor. While biotin deficiency is rare, supplementing can be effective if you have specific genetic disorders, chronic alcohol use, or follow a diet that restricts your intake.
If you have seasonal hair shedding or limited sun exposure, vitamin D could be the issue. Deficiency is common, especially in winter or for people with darker skin. Addressing this can help normalize the hair growth cycle.
For overall hair health, a combination of a balanced diet rich in both nutrients, alongside other key vitamins and minerals like iron and zinc, often provides the best results.

Comparison Table: Biotin vs. Vitamin D for Hair Growth


Feature	Biotin (Vitamin B7)	Vitamin D
Primary Function	Keratin production for hair structure.	Hair follicle cycle regulation and stimulation.
Deficiency Impact	Weak, brittle hair and nails; skin issues.	Hair thinning, slower growth, or alopecia.
Likelihood of Deficiency	Rare, primarily linked to specific genetic or dietary factors.	Relatively common due to lack of sun exposure and diet.
Supplement Effectiveness	Effective for correcting a documented deficiency. Limited evidence for healthy individuals.	Effective for correcting deficiency; may reverse hair loss in deficient individuals.
Best When...	Hair is weak or brittle due to a diagnosed deficiency.	Hair thinning is related to low vitamin D levels.
Interference with Tests	High doses can interfere with lab tests, so consult a doctor.	Can also impact test results, so medical supervision is recommended.

Natural Sources of Biotin and Vitamin D

Before turning to supplements, it's always best to try and meet your nutritional needs through diet and lifestyle.

Biotin-Rich Foods:

Eggs (cooked)
Salmon
Nuts (almonds, peanuts)
Seeds (sunflower seeds)
Sweet potatoes
Beef liver

Vitamin D Sources:

Sun exposure (sensible and safe)
Fatty fish (salmon, tuna, mackerel)
Fortified milk and orange juice
Egg yolks

What to Do If You're Concerned About Hair Loss

For persistent or significant hair loss, consulting a dermatologist or hair specialist is the most effective strategy. A healthcare professional can help you get to the root of the problem by running blood tests to check for specific deficiencies, including those related to iron and thyroid function. They can then recommend the most appropriate course of action, which may or may not involve vitamin supplementation.

Conclusion: A Holistic Approach is Best

So, what is better for hair growth, biotin or vitamin D? The answer isn't that one is inherently superior to the other. Both are critical for healthy hair, but they function in different ways. Biotin plays a structural role by supporting keratin production, while Vitamin D acts as a regulator for the hair follicle's life cycle. The ideal choice for supplementation depends on the root cause of your hair loss. Addressing a deficiency in either through a targeted approach, sometimes with a combination of both under medical guidance, is the most effective strategy. For many, a balanced diet is sufficient, and for others, a blood test is necessary to determine the correct path forward. For further reading on the efficacy of biotin, see this article published on PubMed: A Review of the Use of Biotin for Hair Loss.

Frequently Asked Questions

Vitamin D deficiency is more commonly linked to hair loss than biotin deficiency. While true biotin deficiencies are rare, low vitamin D levels are relatively common, especially in individuals with limited sun exposure, and have been associated with hair thinning and alopecia.

Yes, taking both biotin and vitamin D supplements is generally considered safe and may be beneficial, as they address different aspects of hair health. Vitamin D helps regulate hair follicles, while biotin supports the keratin structure of the hair. It's best to consult a healthcare provider to determine the right dosage for your needs.

Diagnosing a vitamin-related hair loss requires a blood test ordered by a doctor. Symptoms of deficiency can overlap with other conditions, so a clinical diagnosis is necessary. Your doctor will test your levels and rule out other potential causes like genetics or hormonal issues.

For those with a confirmed deficiency, it typically takes 3 to 6 months of consistent supplementation to see noticeable improvements in hair growth and quality. Hair regrowth is a gradual process, and patience is key.

Many people can get adequate amounts of biotin from a balanced diet rich in eggs, nuts, and salmon. However, obtaining sufficient vitamin D from diet alone can be challenging. Safe sun exposure and fortified foods help, but supplementation is often necessary for those with a deficiency.

Excellent food sources of biotin include cooked eggs, salmon, beef liver, nuts like almonds and peanuts, and seeds such as sunflower seeds. Cooking eggs is important as raw egg whites contain a protein called avidin, which can prevent biotin absorption.

The National Institutes of Health (NIH) recommends a daily intake of 600–800 IU (15–20 mcg) for most adults. However, a healthcare provider might recommend a higher dose if a deficiency is detected, often based on individual needs and health history.