If you’re getting your TSH levels checked to monitor your thyroid health, it’s best to get that done in the morning. Otherwise your results may come back normal even though you have hypothyroidism.

All the body’s hormones follow a daily rhythm, including thyroid hormone. This means there are times of the day when it naturally higher or lower. Researchers tested the blood of hypothyroid subjects both before 8 a.m. and again between 2 and 4 p.m.

In hypothyroid patients both untreated and on thyroid medication, TSH dropped was substantially lower during the afternoon test. This means an estimated 50 percent of people with hypothyroidism are not being diagnosed.

In the untreated group, TSH was 5.83 in the morning and 3.79 in the afternoon. In the treated group, TSH was 3.27 in the morning and 2.18 in the afternoon.

A 2004 study also showed late morning, non-fasting TSH was 26 percent lower compared to early morning, fasting TSH. This means even a late morning blood draw could result in a failure to diagnose.

TSH blood test timing and functional medicine ranges

The timing of your blood draw plays an […]