The Hair Loss Blood Panel Your Doctor Should Be Running (But Probably Isn't)
You went to your doctor about hair loss. They glanced at your scalp, said "it's probably genetic," and maybe offered a finasteride prescription. No blood work. No investigation into whether something treatable is driving or accelerating your loss.
This is shockingly common — and it means that correctable causes of hair loss go undiagnosed for years. Here's the blood panel that any serious hair loss evaluation should include.
The 10 Essential Markers
1. Ferritin
Measures iron stores. Optimal for hair: 70-80 ng/mL. Most labs flag as low only below 10-15. The single most commonly deficient marker in people with unexplained hair loss, particularly in women.
2-3. Free T4 and Free T3
Measures active thyroid hormones. TSH alone misses conversion problems and subclinical dysfunction. Both hypo- and hyperthyroidism cause hair loss.
4. TSH
Standard thyroid screening marker. Optimal for hair: 1.0-2.5 mIU/L. Values above 2.5 may warrant further investigation even if technically "normal."
5. TPO Antibodies
Detects Hashimoto's thyroiditis — the most common cause of hypothyroidism. Can be elevated years before TSH becomes abnormal, causing symptoms (including hair loss) that standard screening misses.
6. Vitamin D (25-OH)
Deficiency is endemic and associated with alopecia areata, telogen effluvium, and possibly androgenetic alopecia. Optimal: 40-60 ng/mL. Most people in northern latitudes are below 30.
7. Zinc
Essential for keratin synthesis and follicle cycling. Deficiency is common in vegetarians, people with GI issues, and those taking certain medications. Check serum zinc or RBC zinc.
8. DHEA-S
Adrenal androgen that converts to testosterone and DHT. Elevated DHEA-S in women can indicate adrenal-driven androgen excess as a contributor to hair loss.
9. Testosterone (Free and Total)
Relevant for both men and women. Elevated free testosterone in women can drive androgenetic alopecia. In men, very low testosterone can cause diffuse thinning independent of DHT.
10. CBC with Differential
Complete blood count screens for anemia, infection, and chronic disease — all of which can cause or contribute to hair shedding.
If your primary care doctor won't order this panel, a telehealth provider specializing in hair loss can. Many telehealth platforms now offer comprehensive hair loss workups that include these markers, with results available in days and a follow-up consultation to review findings.
Key Takeaway
- Most doctors run zero hair-specific labs — this misses treatable causes
- Ferritin, thyroid panel, vitamin D, zinc, and hormones are the minimum workup
- Standard "normal" ranges don't reflect optimal levels for hair health
- Correcting a deficiency can produce dramatic improvement without adding medications
- Telehealth platforms can order these labs without an office visit
Explore Your Options
Verified telehealth providers — all links are affiliate partnerships
FDA-approved brand-name hair loss medications via telehealth
Brand-name FDA-approved medications only
Prescription hair loss treatments — finasteride, minoxidil, and combination therapy