If you suspect low thyroid function in spite of normal blood levels, here’s a test you can perform at home. Since the thyroid gland controls all metabolic processes, you can get a pretty good idea of the health of your thyroid gland by measuring your underarm basal (resting) temperature. This is easier with a basal thermometer, but a regular thermometer will do.

To perform the test, shake the thermometer down at night and keep it at your bedside. First thing in the morning, while you’re still in bed and before you move around, put it under your armpit for exactly 10 minutes. Record the temperature and repeat this process for 4 days to get an average temperature reading. Women who are still menstruating should note that only temperatures taken on the first through the fourth day of the cycle are accurate. Normal readings are between 97.8 and 98.2. Temperatures consistently lower than 97.8 degrees suggest inadequate thyroid production.