What to watch with FT3 and Schlaf?

FT3 (free triiodothyronine) is the active thyroid hormone and can influence sleep-wake regulation. Elevated FT3 (e.g., in hyperthyroidism) often causes restlessness, insomnia, and poor sleep quality. Low FT3 (e.g., in hypothyroidism) may lead to fatigue and daytime sleepiness, but can also disrupt sleep architecture. The evidence for a direct FT3–sleep link is moderate: mostly observational studies with confounding factors (stress, caffeine, lifestyle). A home FT3 test (finger-stick) gives an orienting snapshot, not a clinical diagnosis. If values are abnormal or sleep problems persist, see a doctor for a full thyroid panel (TSH, fT4, antibodies). Caveat: FT3 can fluctuate due to inflammation, medications, or fasting. Do not base health decisions solely on home tests.