Description

What This Test Measures

The Total T4 test measures the overall amount of thyroxine (T4) in your blood, including both bound and free hormone. T4 is one of the main hormones produced by the thyroid gland and plays a key role in regulating metabolism, energy levels, and overall body function.

Who Should Consider This Test

  • Fatigue or low energy
  • Unexplained weight gain or weight loss
  • Hair thinning or dry skin
  • Sensitivity to cold or heat
  • Brain fog or sluggish thinking
  • Monitoring known thyroid conditions
  • Follow-up to abnormal TSH results

Why It Matters

Total T4 helps evaluate how well your thyroid is functioning. Abnormal levels may indicate:

  • Hypothyroidism (underactive thyroid)
  • Hyperthyroidism (overactive thyroid)
  • Thyroid hormone binding issues
  • Medication-related changes

This test is often used alongside other thyroid markers such as TSH, Free T4, and Free T3 for a more complete picture.

Preparation

  • Fasting: Not required