--- title: "Which blood tests should you get for dry skin and brittle nails?" type: symptom url: "https://www.test-well.com/symptoms/dry-skin" symptom: Dry skin and brittle nails aliases: - dry skin blood test - brittle nails blood test - dry skin thyroid test - dry skin vitamin deficiency test reviewed_at: 2026-09-06 review_status: reviewed date_published: 2026-09-07 lab_fee_usd: 6 --- # Which blood tests should you get for dry skin and brittle nails? > Dry skin and brittle, ridged or spoon-shaped nails are common and usually environmental, but they are also classic signs of an underactive thyroid, iron deficiency, and low zinc, vitamin D or biotin — and, less often, diabetes or kidney and liver disease. A TSH, ferritin, CBC, zinc, vitamin D and a metabolic panel cover the treatable causes. A rash that is spreading, blistering or painful needs a clinician. ## When should you see a clinician instead of ordering a test? - A rash that is spreading rapidly, blistering, or involves the mouth or eyes - Dry skin with yellowing of the skin or eyes, or dark urine (liver) - Skin changes with unexplained weight loss, fever or night sweats - Nail changes in a single nail with dark streaks or lifting — see a dermatologist ## Why these tests for dry skin and brittle nails? Hypothyroidism slows skin turnover and oil production, producing dry, cool skin, coarse hair and brittle nails; TSH with free T4 is the highest-yield test. Iron deficiency causes brittle or spoon-shaped nails and hair shedding — ferritin catches it before anemia. Zinc, vitamin D, biotin and essential fatty acids all contribute to skin barrier and nail strength. Zinc and vitamin D are the deficiencies most often found; biotin deficiency is rare but the test exists. A metabolic panel and A1c screen for diabetes and kidney or liver disease, which cause dry, itchy skin through other mechanisms. ## Which conditions do these tests help evaluate? - [Thyroid Problems](https://www.test-well.com/conditions/thyroid-problems) — TSH, Free T4/T3 and antibodies to evaluate an under- or over-active thyroid. - [Anemia](https://www.test-well.com/conditions/anemia) — CBC, iron studies, ferritin, B12 and folate to find the cause of fatigue and low energy. - [Hair Loss](https://www.test-well.com/conditions/hair-loss) — Thyroid, iron/ferritin, hormones and vitamins behind unexplained shedding. ## Which tests, and what do they cost? | Test or panel | Type | Price | All-in (one item + $6 fee) | Fasting | Results | | --- | --- | --- | --- | --- | --- | | [Complete Thyroid Panel](https://www.test-well.com/tests/thyroid-complete-panel) | Panel (4 tests) | $109.99 | $115.99 | No | 3–7 business days | | [Vitamin & Mineral Deficiency Panel](https://www.test-well.com/tests/vitamin-mineral-panel) | Panel (9 tests) | $189.99 | $195.99 | No | 3–5 business days | | [Women's Hair Health Panel](https://www.test-well.com/tests/womens-hair-health-panel) | Panel (19 tests) | $469.99 | $475.99 | No | 4–7 business days | | [TSH (Thyroid Stimulating Hormone)](https://www.test-well.com/tests/tsh) | Test | $26.99 | $32.99 | No | 1–3 business days | | [Free T4 (Thyroxine)](https://www.test-well.com/tests/free-t4-test) | Test | $23.99 | $29.99 | No | 1–3 business days | | [Ferritin](https://www.test-well.com/tests/ferritin) | Test | $24.99 | $30.99 | No | 1–3 business days | | [CBC with Differential](https://www.test-well.com/tests/cbc-with-differential) | Test | $21.99 | $27.99 | No | 1–3 business days | | [Zinc](https://www.test-well.com/tests/zinc) | Test | $26.99 | $32.99 | Yes | 3–6 business days | | [Vitamin D, 25-Hydroxy](https://www.test-well.com/tests/vitamin-d) | Test | $41.99 | $47.99 | No | 1–3 business days | | [Comprehensive Metabolic Panel](https://www.test-well.com/tests/comprehensive-metabolic-panel) | Test | $22.99 | $28.99 | Yes | 1–3 business days | | [Hemoglobin A1c](https://www.test-well.com/tests/hemoglobin-a1c) | Test | $21.99 | $27.99 | No | 2–4 business days | | [Biotin (Vitamin B7)](https://www.test-well.com/tests/biotin) | Test | $259.99 | $265.99 | No | 3–7 business days | | [Omega-3 Index](https://www.test-well.com/tests/omega-3-index) | Test | $69.99 | $75.99 | No | 7–10 business days | Prices are cash-pay; every order adds one $6.00 lab processing fee. Physician authorization included. ## Common questions ### Can dry skin be a sign of a thyroid problem? Yes — dry, cool, pale skin with brittle nails and hair is one of the classic presentations of hypothyroidism, usually with fatigue, weight gain or feeling cold. A TSH answers it. ### What deficiency causes brittle nails? Iron deficiency is the most common lab-confirmable cause, followed by zinc; biotin deficiency is rare in people eating a normal diet. Frequent wetting and drying of the hands is the most common non-deficiency cause. ### Should I take biotin for my nails? Only after testing — biotin supplements interfere with thyroid, troponin and hormone assays, and evidence for nail benefit is thin. If you already take it, stop 72 hours before any blood draw. ## Related - [What blood tests should you get for fatigue?](https://www.test-well.com/symptoms/fatigue) - [Which blood tests help explain brain fog?](https://www.test-well.com/symptoms/brain-fog) - [What blood tests should you get for hair loss?](https://www.test-well.com/symptoms/hair-loss) - [What blood tests check for causes of unexplained weight gain?](https://www.test-well.com/symptoms/weight-gain) - [All symptoms](https://www.test-well.com/symptoms) - [Browse by condition](https://www.test-well.com/conditions) ## Sources - [American Academy of Dermatology — Dry skin: who gets and causes](https://www.aad.org/public/diseases/a-z/dry-skin-causes) - [American Thyroid Association — Hypothyroidism](https://www.thyroid.org/hypothyroidism/) - [NIH ODS — Zinc fact sheet](https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-06. Review policy: https://www.test-well.com/editorial-policy Canonical page: https://www.test-well.com/symptoms/dry-skin Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.