How often should I monitor TSH levels in a patient who is stable on levothyroxine therapy for hypothyroidism?

For a patient who is stable on levothyroxine therapy for hypothyroidism, thyroid-stimulating hormone (TSH) levels should be monitored annually once stability is confirmed by two similar TSH measurements within the reference range taken 3 months apart.

Initially, TSH should be measured every 3 months until the level stabilises (defined as two similar measurements within the reference range 3 months apart). After this, annual monitoring is recommended.