Anirva sells Hair Radiance with Probiotics, a dietary supplement. This article shares research for general education and is not medical advice. These statements have not been evaluated by the Food and Drug Administration.
Vitamin D is often called the sunshine vitamin, and many people know it for strong bones. So when hair starts thinning, it is natural to wonder whether vitamin D plays a part too. The research suggests it may, especially for people who are low in it. That said, the studies are still growing, and the clearest step is to find out your own level first. Here is what we know.
In this article
Key Takeaways
- Low vitamin D has been linked to some kinds of hair shedding. A 2019 review called the results mixed and said larger trials are needed.
- Many people run low. The NIH lists older adults, people with darker skin and people who get little sun among those at risk.
- A blood test tells you where you stand. The NIH considers 20 ng/mL (50 nmol/L) or above adequate for most people.
- More is not better. The adult upper limit is 100 mcg (4,000 IU) a day, and too much can cause harm.
- Vitamin K2 is often paired with D3, but we found no research on the pair for hair.
What Vitamin D Has to Do With Hair
Vitamin D acts in many parts of the body, not only the bones. Several studies have found lower vitamin D levels in people with certain types of hair shedding than in people without it. A 2019 review in Dermatology and Therapy looked at this research. It called the results mixed, and it said larger trials are needed to know whether taking vitamin D helps hair.
So the link is real enough to take seriously, but not strong enough to promise results. The research is still growing, and the most useful step today is to check whether you are low.
Who May Run Low on Vitamin D
Your skin makes vitamin D in sunlight, and a few foods provide it. The NIH Office of Dietary Supplements lists these groups as more likely to run low:
- Older adults, because skin makes less vitamin D with age
- People who get little sun, or who keep most of their skin covered
- People with darker skin
- People with conditions that affect fat absorption, such as Crohn's disease or celiac disease
- People with obesity, or who have had gastric bypass surgery
If one of these fits you, and your hair is thinning, a vitamin D test is a sensible thing to ask about.
What Your Blood Test Means
The usual test measures 25-hydroxyvitamin D, often written 25(OH)D. Results may be in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). The NIH uses these ranges:
| Level | What the NIH Says |
|---|---|
| Below 12 ng/mL (30 nmol/L) | Linked to vitamin D deficiency |
| 12 to under 20 ng/mL (30 to under 50 nmol/L) | Generally not enough for bone health |
| 20 ng/mL (50 nmol/L) or above | Generally enough for bone health |
| Above 50 ng/mL (125 nmol/L) | Linked to possible harmful effects |
Source: NIH Office of Dietary Supplements, Vitamin D fact sheet.
Your doctor can explain what your number means for you, and whether a supplement makes sense.
How Much Vitamin D You Need
The NIH sets the recommended amount for adults at 15 mcg (600 IU) a day up to age 70, and 20 mcg (800 IU) after 70. The adult upper limit is 100 mcg (4,000 IU) a day from all sources. Vitamin D labels often show both units, and 1 mcg equals 40 IU.
Food can help. These amounts are from the NIH:
| Food | Vitamin D |
|---|---|
| Rainbow trout, farmed, cooked, 3 ounces | 16.2 mcg (645 IU) |
| Sockeye salmon, cooked, 3 ounces | 14.2 mcg (570 IU) |
| White mushrooms exposed to UV light, raw, ½ cup | 9.2 mcg (366 IU) |
| Milk, 2%, fortified, 1 cup | 2.9 mcg (120 IU) |
| Egg, 1 large, scrambled | 1.1 mcg (44 IU) |
Source: NIH Office of Dietary Supplements.
The NIH also notes that fat in a meal helps the body absorb vitamin D, and that vitamin D3 tends to raise blood levels more than vitamin D2.
When More Is Not Better
Because vitamin D is stored in the body, too much can build up. The NIH lists nausea, vomiting, muscle weakness, confusion, loss of appetite, dehydration, excessive thirst and kidney stones among the signs of too much. Toxicity is uncommon, and it usually comes from supplements rather than food or sun. Still, if you take more than one product, it is worth adding up the vitamin D across all of them.
Why Take K2 With Vitamin D3?
Many people see vitamin D3 and K2 sold together and wonder why. Both vitamins play a part in how the body uses calcium, and the NIH notes that vitamin K is important for healthy bones and for blood clotting. That is the usual reason for pairing them.
We found no research on taking K2 with D3 for hair. Hair Radiance does not contain vitamin K. One point matters for safety. The NIH notes that people who take warfarin, a blood thinner, should keep their vitamin K intake steady, because a sudden change can affect clotting. So if you take a blood thinner, talk with your doctor before adding K2.
Vitamin D Is One Part of Hair Radiance
Hair Radiance contains 62.5 mcg (2,500 IU) of vitamin D3 per serving of three vegetarian capsules. That is above the daily recommendation and below the adult upper limit of 4,000 IU. The label suggests taking the capsules with food, which may help absorption.
Good to Know
If You Are Deciding
It can help to start with a blood test, especially if you are in one of the groups more likely to run low. If your level is low, your doctor can suggest how much to take and when to recheck. If your level is already adequate, extra vitamin D is less likely to change your hair.
Whatever you decide, give it time. Hair grows about half an inch a month, according to MedlinePlus, so any change takes a few months to show.
The Short Version
Studies have linked low vitamin D to some kinds of hair shedding, though a 2019 review called the results mixed. Many people run low, especially older adults, people with darker skin and people who get little sun. A blood test is the clearest first step, and 20 ng/mL or above is generally adequate. Stay under 4,000 IU a day from all sources unless your doctor advises otherwise.
Frequently Asked Questions
Does vitamin D help hair growth?
How much vitamin D should I take for hair?
Can low vitamin D cause hair loss?
Why take K2 with vitamin D3?
Is 2,500 IU of vitamin D a day safe?
Is vitamin D3 better than D2?
References
- Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The role of vitamins and minerals in hair loss: a review. Dermatol Ther (Heidelb). 2019;9(1):51-70. pubmed.ncbi.nlm.nih.gov DOI 10.1007/s13555-018-0278-6; PMID 30547302.
- NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. ods.od.nih.gov
- NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Consumers. ods.od.nih.gov
- NIH Office of Dietary Supplements. Vitamin K: Fact Sheet for Consumers. ods.od.nih.gov
- MedlinePlus, US National Library of Medicine. Hair Problems. medlineplus.gov
Hair Radiance with Probiotics
2,500 IU vitamin D3, part of a full formula
Vitamins, minerals, Ayurvedic herbs and three probiotic strains — each with its own labeled amount, at or above the Daily Value.
See Hair Radiance →Written by the Anirva Editorial Team | Reviewed by [REVIEWER NAME AND CREDENTIAL REQUIRED] | Last reviewed: September 29, 2026
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
