Everyday Health Guide

Measures CD4 (a type of white blood cell that fights infection and is closely monitored in HIV management). No fasting is required. A standard blood draw is performed.

Measures total testosterone (the overall amount of the primary male sex hormone in the blood, though it is also present in females). Blood is best drawn in the morning when levels are highest. A standard blood draw is performed.

A throat culture (a swab test to grow and identify bacteria causing a sore throat) is performed by rubbing a sterile cotton swab against the back of the throat and tonsils. No fasting is required.

Measures thyroglobulin (a protein produced by the thyroid gland, used as a tumor marker to monitor for thyroid cancer recurrence after surgery). No fasting is required. A standard blood draw is performed.

Detects TPO (an enzyme in the thyroid gland; antibodies against it indicate the immune system is mistakenly attacking the thyroid). No fasting is required. A standard blood draw is performed.

Measures TSH (a hormone produced by the pituitary gland that tells the thyroid to produce thyroid hormones). Fasting is usually not required, but some doctors prefer morning testing. A standard blood draw is performed.

Measures tTG (an enzyme targeted by the immune system in celiac disease). You must be eating a gluten-containing diet for the test to be accurate. No fasting is required. A standard blood draw is performed.

Measures TIBC (the blood's capacity to bind iron with transferrin, a protein that transports iron). Fasting for 8–12 hours is usually recommended. A standard blood draw is performed.

Measures the total amount of two classes of proteins (albumin and globulin) found in the fluid portion of blood. Fasting for 8 hours may be required. A standard blood draw is performed.

A toxicology screen (a test to detect the presence of drugs or poisons in the body) analyzes a urine sample for substances like opioids, amphetamines, or benzodiazepines. A clean catch mid-stream sample is preferred.

Measures transferrin (a protein that transports iron through the blood). It is often ordered alongside serum iron and TIBC tests. Fasting for 8–12 hours is usually recommended. A standard blood draw is performed.

A transvaginal ultrasound (an imaging test where a lubricated probe is gently inserted into the vagina to view pelvic organs like the uterus and ovaries) provides more detailed images than an abdominal ultrasound. You may be asked to empty your bladder beforehand.

A TMT (Treadmill Test, which monitors the heart's response to physical exertion) involves walking on a treadmill while an ECG (electrocardiogram) and blood pressure are continuously monitored. Wear comfortable walking shoes and avoid heavy meals beforehand.

A TPHA (a confirmatory blood test for syphilis infection) detects specific antibodies against the bacteria that cause syphilis. It is usually done after a positive VDRL screening test. No fasting is required. A standard blood draw is performed.

Measures triglycerides (a type of fat found in the blood). High levels can increase the risk of heart disease. Fasting for 9–12 hours is strictly required. A standard blood draw is performed.

Checks for TB exposure by injecting a small amount of tuberculin fluid just under the skin of the forearm. The injection site must be examined by a healthcare professional 48 to 72 hours later to measure any swelling.

An IGRA (a blood test that checks for TB infection by measuring the immune system's reaction to TB proteins) is more specific than the traditional skin test. No fasting is required. A standard blood draw is performed.

Measures CA 15-3 (Cancer Antigen 15-3, a protein that can be elevated in breast cancer). It is primarily used to monitor treatment response, not for initial screening. No fasting is required. A standard blood draw is performed.