Rapid weight loss, very low-calorie or crash diets, and low iron stores (ferritin) are well-known triggers of telogen effluvium. Hair is a low-priority tissue, so when the body is short on energy, protein, iron, zinc or vitamin D, it sheds. This shows up as diffuse thinning a couple of months after the dietary change, and it reverses once nutrition is restored. Adequate protein (often under-eaten when dieting) and correcting low ferritin are the highest-yield fixes.
The catch: supplements only help if you're actually deficient — taking iron or 'hair vitamins' when your levels are normal does little and can cause harm (too much iron is toxic; biotin can skew lab tests including thyroid and troponin). So the evidence-based move is to eat enough, and test ferritin, vitamin D and thyroid rather than guess. If you also have a receding hairline or crown thinning, that's pattern loss and needs its own treatment.
Try the free self-check →Sources: AGA review (CCID) ↗
FAQ
Do hair vitamins like biotin work?
Only if you have a real deficiency, which is rare. Biotin supplements don't help most people and can interfere with blood tests. Fix a proven shortfall (iron, protein, vitamin D) instead of guessing.
What iron level matters for hair?
Ferritin (iron stores) is the key number; many dermatologists aim for at least 30-50 ng/mL for hair, higher than the lab's 'normal' floor. Ask for a ferritin test if you shed and may be low.
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⚠️ When to see a doctor — don’t self-treat
- Sudden patchy or circular bald spots
- Redness, scaling, pus, pain or itch (possible scarring alopecia — treat urgently)
- Broken hairs or rapid loss
- Loss with body-wide signs (weight loss, fatigue, cycle changes, acne, extra hair)
- Loss right after a new medication
- Any hair loss in a child