Quest Diagnostics Thyroid TSH Function Test
Type
Blood Testing
Biomarkers
3
Duration
30 min
Results
48 hours
This thyroid function test measures TSH levels in your blood to help determine if your thyroid gland is functioning properly and identify signs of hypothyroidism or hyperthyroidism.
Noticeable changes in your metabolism (e.g., weight, temperature, and energy) may be an indication of abnormal levels of thyroid stimulating hormone (TSH) in your blood. This thyroid function test measures the TSH levels in your blood to help identify these abnormalities. High TSH levels may indicate an overactive thyroid (i.e., hyperthyroidism), while low TSH levels may suggest an underactive thyroid (i.e., hypothyroidism). In either case, T4 reflex testing will be performed at no additional cost to help identify a possible thyroid disorder. Thyroid disorders can affect any system of your body and treatment will depend on the specific thyroid condition. An undiagnosed thyroid disorder may put you at risk for cardiovascular diseases, osteoporosis, infertility, and other serious conditions; most thyroid conditions can be managed with medication.
Key Details
- Biomarkers
- 2–7 thyroid markers
- Fasting Required
- No
- Sample Type
- Blood draw
- Turnaround
- 24–48 hours
- Common Use
- Thyroid function, autoimmune screening
Who Is This For?
Anyone experiencing unexplained fatigue, weight changes, hair loss, cold sensitivity, or mood disturbances. People with a family history of thyroid disease or autoimmune conditions. Women planning pregnancy, as thyroid function is critical for fetal brain development. Anyone who has had a 'normal' TSH result but still suspects thyroid dysfunction.
What's Included
Preparation Required
No fasting required for a standalone thyroid panel. If you take thyroid medication (levothyroxine/Synthroid), take your dose after the blood draw, not before — taking it beforehand can temporarily spike T4 levels and skew results. Morning testing is recommended for the most consistent TSH readings, as TSH follows a circadian rhythm and peaks overnight.
Biomarkers Tested
3The primary screening test for thyroid function. TSH is produced by the pituitary gland to regulate thyroid hormone production. High TSH indicates an underactive thyroid (hypothyroidism), while low TSH suggests an overactive thyroid (hyperthyroidism).
The unbound, active form of the main thyroid hormone T4. Free T4 directly reflects thyroid gland output and is used alongside TSH to diagnose and monitor thyroid disorders.
The active form of thyroid hormone responsible for regulating metabolism, energy, and body temperature. Free T3 is converted from T4 in tissues and is three to four times more potent than T4.
+ $6.00 Physician Service Fee
- Category
- Diagnostic
- Sample Type
- Blood draw
- Duration
- 30 min
- Results
- 48 hours