Thyroid-Stimulating Hormone (TSH) Blood Test

The TSH Test measures pituitary output that regulates thyroid hormone production. When thyroid hormones (T3/T4) are low, TSH rises; when they’re high, TSH falls. TSH is a front-line thyroid screen and is best interpreted with Free T4 and, when indicated, Free T3.

Why Measure TSH?

Thyroid function: Evaluate fatigue, weight change, temperature intolerance, hair/skin changes, or cycle changes.
Treatment monitoring: Adjust thyroid therapy with trend data.

Preparation & Notes

Fasting is usually not required. High-dose biotin may interfere with some immunoassays—pause only if your clinician advises. Test at a similar time of day for trend consistency.

How the PlexusDx Test Works

At-home collection;
prepaid mailer;
~2 business-day results;
direct order; HSA/FSA eligible.

FAQ

Normal TSH but symptoms? Reviewing Free T4/Free T3, meds, iron status, and timing can clarify the picture—discuss with your provider.