Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 10/6/2021
Looking a little thin up top? Hair loss can occur for a variety of reasons, the most common of which is hormonal hair loss caused by male pattern baldness.
Other common causes of hair loss include stress and, in some cases, deficiencies of important vitamins and minerals.
If you’ve searched online for information about vitamins and hair loss before, you might have heard of a link between vitamin D and hair loss.
Although research is somewhat limited, there’s evidence that vitamin D deficiency can affect healthy hair growth, potentially resulting in shedding, thinning and patchy hair loss that affects certain parts of your scalp.
Below, we’ve discussed what vitamin D is and how it fits into the hair growth process.
We’ve also explained how vitamin D deficiency may affect your hair, as well as what you can do to make sure you have optimal vitamin D levels throughout the year.
According to the National Institutes of Health, Vitamin D is an essential, fat-soluble vitamin that plays a role in numerous biological processes within your body.
Unlike most vitamins, vitamin D isn’t commonly found in foods. While some foods, such as milk, soy and certain types of fish, contain vitamin D, most vitamin D is produced endogenously when UV rays from sunlight come into contact with your skin.
In its natural form, vitamin D is biologically inert. To use vitamin D, your body needs to convert it into a usable form using the liver and kidneys.
This complex, multi-step process is referred to as hydroxylation, and allows your body to use vitamin D for a variety of important processes.
Vitamin D plays a role in countless biological processes within your body. It’s responsible for:
Promoting calcium absorption (keratinocyte differentiation)
Ensuring healthy bone growth and remodeling
Modulating cell growth
Maintaining a healthy immune system
Vitamin D also plays a key role in preventing certain diseases. People with low levels of vitamin D have an increased risk of developing rickets and osteomalacia — two diseases that can affect the health and integrity of your bones.
Low levels of vitamin D are also linked to certain forms of hair loss — a topic we’ve discussed in more detail below.
Research has shown that people who are deficient in vitamin D often experience some degree of hair loss.
For example, one study published by the National Center for Biotechnology Information of women aged between 18 and 45 found that low levels of vitamin D2 were associated with two common types of hair loss.
A separate study published in 2014 by the National Center for Biotechnology Information found that vitamin D deficiency is linked to hair loss, specifically alopecia areata — a form of patchy hair loss that’s caused by an autoimmune disorder.
Although the precise role of vitamin D in hair growth isn’t well understood, more National Center for Biotechnology Information research shows that vitamin D receptors play an important role in the anagen phase of the hair follicle cycle — the phase in which new hairs grow from the follicle to their full length.
In short, vitamin D deficiency definitely appears to be associated with hair loss. However, being deficient in vitamin D isn’t the only reason you may lose hair – male pattern baldness (androgenetic alopecia) and stress (telogen effluvium) can play a role. Learn more about common causes of hair loss in our guide.
If you’re shedding more hair than normal and think that you could be deficient in vitamin D, the best thing to do is to talk to a healthcare professional.
Your healthcare provider will be able to diagnose vitamin D deficiency via a 25-hydroxy vitamin D blood test.
This is a type of blood test that checks for 25-hydroxyvitamin D — a common form of vitamin D that circulates in your blood.
Vitamin D deficiency is surprisingly common. According to the book, Vitamin D Deficiency, up to one billion people worldwide, approximately 13 percent of the world’s entire population, are deficient in vitamin D.
If you’re severely deficient in vitamin D, you may notice certain symptoms other than hair loss. According to the Cleveland Clinic, common symptoms of vitamin D deficiency include:
Muscle aches and cramps
Bone pain or weakness
Slow healing of cuts and wounds
Changes in your mood (including depressed or anxious mood)
High blood pressure
Certain factors, such as your age, ethnicity and habits, may increase your risk of being deficient in vitamin D. You may have a higher risk of vitamin D deficiency if you:
Spend too little time outdoors in direct sunlight. Low sunlight exposure reduces your body’s ability to produce vitamin D naturally. If you spend lots of time inside away from natural sunlight, you may have a higher risk of developing vitamin D deficiency.
Live in an area with relatively little sunlight. Certain areas receive less sunlight than others, making it harder to produce vitamin D from sun exposure. Seasonal factors can also affect your exposure to sunlight and production of vitamin D.
Don’t get enough vitamin D from your diet. Certain foods, such as fish, cheese, milk and eggs, contain vitamin D. We’ve listed these foods in more detail below. If you rarely eat foods that contain vitamin D, you may have a higher risk of vitamin D deficiency.
Have dark skin. People with darker skin pigmentation produce less vitamin D naturally in response to sunlight. If you’re African American or Hispanic, you may have a higher risk of developing vitamin D deficiency than a person with a lighter skin tone.
Are older. Older adults produce less vitamin D when exposed to sunlight. The kidneys also become less efficient at converting vitamin D into its active form with age, meaning older adults are more likely to develop vitamin D deficiency.
Are obese. Body fat binds to vitamin D, preventing it from getting into the blood. In one study, researchers found that the prevalence of vitamin D deficiency is 35 percent higher in obese people compared to people in an ideal weight range.
Have Crohn's disease or celiac disease. These diseases may affect the absorption of certain nutrients, resulting in lower vitamin D levels.
Use certain medications. Some medications may interfere with vitamin D metabolism and absorption, including some anti-seizure and antifungal medications, glucocorticoids, cholestyramine and certain medications used to treat HIV/AIDS.
Have had gastric bypass surgery. According to Annals of Surgery, people who have gastric bypass surgery often only consume 50 percent of the recommended daily vitamin D intake, increasing your risk of vitamin D deficiency if you’ve undergone this procedure.
Have another health condition. Other health conditions that can increase your risk of vitamin D deficiency include osteoporosis, skin cancer, chronic kidney or liver disease, lymphomas, hyperparathyroidism, sarcoidosis, tuberculosis, histoplasmosis and others.
Vitamin D deficiency is also common in breastfed infants. If you have an infant who is breastfed, your healthcare provider may recommend providing them with a vitamin D supplement to avoid developing a vitamin D deficiency.
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If you’ve been diagnosed with a vitamin D deficiency, your healthcare provider will likely recommend the use of a vitamin D supplement.
They may also recommend making some changes to your diet and habits to increase the amount of vitamin D you consume via food or produce naturally.
You can get more vitamin D by:
The Harvard School of Public Health says the recommended dietary allowance for vitamin D is 600 IU daily for adults 19 years and older.
For adults 70 and up, it’s 800 IU daily. If you don’t get much vitamin D naturally, using a supplement such as vitamin D3 may be helpful. Vitamin D supplements are inexpensive and widely available.
If you have a high risk of vitamin D deficiency due to a health condition or other factor, your healthcare provider may suggest using a larger dosage of vitamin D than the typical recommended dietary allowance.
For optimal results, follow your healthcare provider’s instructions and use your vitamin D supplement only as recommended. Do not take excessive amounts of vitamin D from a supplement, as this may cause health problems.
Some foods are rich in vitamin D, making them a good natural source of this vitamin. Foods that contain vitamin D include fatty fish, such as tuna, avocado, nuts, salmon or mackerel, cheese, egg yolks, mushrooms and beef liver.Fortified foods may also contain vitamin D. Certain types of milk, yogurt and other dairy products, as well as soy drinks, breakfast cereals and orange juices, may contain added vitamin D. You can often find this information on the product’s nutrition facts label.
Your body produces its own vitamin D naturally in the skin when it’s exposed to UV radiation from sunlight. Spending too much time in direct sunlight isn’t good for your skin, but a small amount of sun exposure can help to produce vitamin D naturally.
According to the Harvard Medical School, 10 to 15 minutes of sun exposure a few times a week is normally enough to maintain healthy levels. And remember — always wear sunscreen.
Although it’s important to take in a certain minimum amount of vitamin D for optimal health, it’s definitely possible to get too much vitamin D.
Your body limits the amount of vitamin D that it will produce due to sun exposure. This means that there’s no real risk of you “overdosing” on vitamin D if you spend too much time outside on a sunny day, although there are obviously other risks involved in excessive sun exposure.
However, overusing vitamin D supplements can cause something called vitamin D toxicity — a potentially harmful condition that can cause nausea, vomiting, constipation, weakness, weight loss, reduced appetite, heart rhythm problems and even damage to your kidneys.
To avoid vitamin D toxicity, only use vitamin D supplements as recommended by your healthcare provider or other healthcare professional.
If you’ve noticed your hair shedding or looking thin and think that it could be due to a vitamin D deficiency, talk to your healthcare provider.
They will be able to test you for a vitamin D deficiency and, if appropriate, may recommend using a vitamin D supplement.
You may also be able to increase your vitamin D levels by changing your diet to include more foods that contain vitamin D, or by spending 10 to 15 minutes outside during sunny weather a few times each week.
There are numerous reasons that you might lose hair. While a vitamin D deficiency could be a cause of your hair loss, it may also be due to male pattern baldness, stress, use of medication or many other factors.
Dealing with hair loss can be a stressful experience. Luckily, several science-backed hair loss treatment options are available that can help you slow down or stop hair loss.
Some might even help you with hair regrowth in areas of your scalp where your hair has started to thin.
Our guide to minoxidil and finasteride goes into detail on the science behind two of the world’s most effective hair loss treatments to explain how they work and how you can use them to take control over your hair for good.