Description
Why It’s Done:
Doctors may order an FT4 test to:
• Evaluate thyroid function and diagnose thyroid disorders such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid)
• Monitor ongoing thyroid treatment
• Assess abnormal TSH (thyroid-stimulating hormone) levels
• Help determine the cause of symptoms like fatigue, weight changes, depression, or temperature sensitivity
• Screen newborns for congenital hypothyroidism
Preparation:
• Fasting: Not required.
• Medications: Inform your healthcare provider about all medications and supplements you’re taking, especially thyroid medications, steroids, or estrogen-containing drugs, as they may affect results.
• Timing: Blood can be drawn at any time of day; however, morning collection is often preferred for consistency.
• No special dietary restrictions or lifestyle changes are needed unless advised by your doctor.
