Why is my hair falling out and what can I do about it?

Hair loss in adults — particularly diffuse thinning rather than pattern baldness — is almost always driven by internal biology. Hair follicles are among the most metabolically active cells in the body and are highly sensitive to internal imbalance. The most common drivers include:

• Thyroid dysfunction — both hypothyroidism and hyperthyroidism disrupt the hair growth cycle; even subclinical thyroid imbalance can cause significant shedding
• Iron and ferritin deficiency — ferritin (stored iron) is critical for hair follicle function; levels below 70 ng/mL are associated with hair loss even when hemoglobin is normal
• Hormonal shifts — elevated androgens (testosterone, DHEA-S) miniaturize follicles; declining estrogen during perimenopause reduces the growth phase of the hair cycle
• Chronic inflammation — systemic inflammation disrupts follicle cycling and can trigger telogen effluvium (sudden, diffuse shedding)
• Nutrient deficiencies — zinc, biotin, vitamin D, and amino acid deficiencies all impair hair structure and growth

The frustrating reality is that standard labs often miss the specific markers that matter. A normal TSH does not rule out thyroid-related hair loss if free T3 is suboptimal. Normal hemoglobin does not rule out ferritin deficiency. These markers need to be evaluated together, in the context of your full clinical picture, not in isolation.

Most cases of diffuse hair loss are reversible once the underlying driver is identified and addressed — but the window for intervention matters. Earlier evaluation produces better outcomes.