What Vitamin Deficiency Causes Hair Loss?

What Vitamin Deficiency Causes Hair Loss?

The vitamin and mineral deficiencies most often linked to hair loss are iron (ferritin), vitamin D, zinc, and B vitamins — especially B12, folate, and biotin. Severe calorie restriction or protein deficiency can also trigger shedding. No single deficiency causes all hair loss, and in many cases a deficiency is only one contributing factor rather than the whole story.

How Do Vitamin Deficiencies Lead to Hair Loss?

Hair follicles are among the most metabolically active tissues in the body. They divide quickly and need a steady supply of oxygen, protein, and cofactors like iron, zinc, and vitamin D to keep cycling through growth, transition, and rest phases. When a nutrient runs low, the follicle can be pushed into the resting (telogen) phase early, and shedding shows up roughly two to four months later.

• Iron is needed to make hemoglobin, which carries oxygen to the follicle. Low ferritin starves the follicle of oxygen.
• Vitamin D helps regulate the hair growth cycle and the creation of new follicles.
• Zinc supports DNA and protein synthesis in the follicle and helps repair tissue.
• B12 and folate are required for red blood cell production and cell division.
• Biotin is a coenzyme for keratin production, though true biotin deficiency is rare.
• Protein and calories provide the amino acids that build the hair shaft itself.

Which Vitamin and Mineral Deficiencies Are Linked to Hair Loss?

Not every deficiency affects hair the same way. Some cause diffuse shedding across the whole scalp, while others mainly weaken the hair shaft. The table below summarises the main nutrients studied in hair loss research.

What Are the Most Common Deficiencies Behind Hair Loss?

In clinical practice, a handful of deficiencies come up again and again. Iron deficiency without anemia is probably the single most common one seen in women with unexplained shedding. Vitamin D insufficiency is also extremely widespread, especially in northern latitudes and in people who cover their skin or work indoors.

• Low ferritin (iron stores) — often under 30 ng/mL is considered low for hair, even if hemoglobin is normal.
• Vitamin D insufficiency — common in winter, in office workers, and in people with darker skin.
• Zinc deficiency — more common in vegetarians, people with GI conditions, and heavy alcohol users.
• Vitamin B12 deficiency — seen in vegans, older adults, and long-term metformin users.
• Folate deficiency — linked to poor diet, alcohol use, and pregnancy.
• Protein-energy malnutrition — from crash dieting or eating disorders.

Who Is Most at Risk for Deficiency-Related Hair Loss?

Anyone can develop a deficiency, but certain groups are much more likely to. If you fall into one or more of these categories and you're shedding more than usual, a blood test is a reasonable next step.

• Women with heavy menstrual bleeding or fibroids.
• Vegans and vegetarians who don't supplement B12, iron, or zinc.
• People who've had bariatric surgery or gut conditions like celiac or Crohn's.
• Anyone on a very low-calorie or keto-style crash diet.
• Pregnant and postpartum women, whose nutrient demands spike.
• Older adults, who absorb B12 and vitamin D less efficiently.
• People with darker skin living in low-sun regions.
• Heavy alcohol users, who deplete folate, B12, and zinc.

How Are Vitamin Deficiency Hair Loss Diagnosed and Treated?

Diagnosis starts with a blood panel and a scalp exam. Treatment depends on what the labs show — there's no point megadosing biotin if your ferritin is the problem. Here's the usual step-by-step approach a dermatologist or trichologist follows.

• Step 1: History — diet, periods, medications, recent illness, weight loss, family history of pattern baldness.
• Step 2: Scalp exam — look at shedding pattern, hair pull test, and whether follicles are miniaturised (which points to genetic loss).
• Step 3: Blood tests — CBC, ferritin, vitamin D, zinc, B12, folate, thyroid, and sometimes testosterone/DHEA in women.
• Step 4: Correct the deficiency — oral supplements, diet changes, or injections for B12 if absorption is poor.
• Step 5: Recheck levels after 3–6 months and adjust the dose.
• Step 6: If shedding continues after levels normalise, consider other causes like androgenetic alopecia, thyroid disease, or telogen effluvium from stress.

When Should You See a Specialist for Hair Loss?

See a doctor or dermatologist if shedding lasts more than three months, if you can see scalp through your hair, if you have patches of complete baldness, or if you have other symptoms like fatigue, weight change, or irregular periods. A specialist can tell the difference between deficiency-related shedding and genetic pattern hair loss — and that distinction matters, because the treatments are completely different.

If your levels are normal and the diagnosis is genetic hair loss, a hair transplant may be worth exploring. You can browse vetted clinics and compare options in the Clinic Reccy directory.

Frequently Asked Questions

Where to Get Help

Start with your GP or a dermatologist for blood work. If your levels come back normal and you're still losing hair, it's worth getting a proper scalp evaluation. Clinic Reccy lists hair restoration clinics and specialists you can compare directly.