Doctors use a blood test that measures the level of thyroid stimulating hormone (TSH) to adjust the dose of thyroid pills. Experts don't always agree about the normal range for TSH levels. If your TSH level is higher than 3.0 and you still have dry skin or other symptoms of an underactive thyroid in spite of taking thyroid pills, your doctor may want to increase your dose.
Hypothyroidism might not be your only reason for dry skin.