Acne or dark patches on neck? Blood tests that may help

Teenage acne is usually just hormones settling down, but acne that starts or continues in adulthood, especially along the jaw, can be linked with hormonal imbalance. Dark, velvety patches on the back of the neck, underarms or groin (acanthosis nigricans) are a well-known sign of insulin resistance. Blood tests help your dermatologist look for these internal causes.

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Tests to ask about

HbA1c

Checks for prediabetes, often linked with dark neck patches.

₹420 Book Details

Fasting insulin

High insulin points towards insulin resistance.

₹460 Book Details

Testosterone

Raised levels in women can cause acne and extra hair.

₹735 Book Details

PCOD profile (women)

Checks the main hormones together.

₹2,350 Book Details

Thyroid profile (T3, T4, TSH)

Thyroid imbalance often shows on the skin.

₹1,200 Book Details

Common reasons doctors look for

Insulin resistance or prediabetes – dark velvety neck patches
PCOD in women – acne on jaw and chin, extra facial hair
Thyroid problems – dry skin, itching, puffiness
Low vitamin B12 or D, sometimes linked with pigmentation
Skin care products, sweat and friction
Stress and poor sleep

How to prepare

For fasting sugar and fasting insulin, fast 8–12 hours (water is fine) and give the sample in the morning. Hormone tests for women may need a specific day of the cycle – ask your doctor.

When to see a doctor

See a dermatologist for painful, deep or scarring acne, or patches that spread quickly. See a doctor urgently for a rapidly spreading rash with fever, blisters, peeling skin, or swelling of lips and eyes. Dark patches appearing suddenly in an older adult also need a doctor's check.