Why check basal body temperature (BBT)? Part 1
BBT is arguably the most accurate widely available test to monitor basal metabolic rate (how much energy your body produces at rest). Metabolism is primarily determined by:
a) how well your thyroid is functioning,
b) how well your body is converting inactive thyroid hormones into active T3, and
c) how well your cells are able to respond to T3. Obviously this is a complex process, and the "big picture" is often missed by relying on standard laboratory tests such as TSH.
Dr. Frank Shallenberger’s Bio-Energy Test, which directly measures O2 consumption and CO2 production and calculates an amazing array of metabolic information, is probably the gold standard metabolic test, but it's not widely available.