Basal body temperatures (BBTs) as backup to pills
Can you (reliably) take BBT temperatures while you're taking birth control pills? I'd like to do this as a back up method to my pills, but don't want to if it will alter the temps either way...
That's an interesting question I don't think I've ever had asked before. I'm not sure, but I suspect the progestin in the pill would alter the early temps to make them higher.
On the other hand, if you had a breakthrough ovulation on the pill it could well show a biphasic curve. If you took BBTs for two months and they were flat, I would quit taking them.
The failure rate of BC pills is about 1-3% overall but if there is perfect use (no pills missed) the failure rate is only about 3/1000.
It seems if you are compulsive enough to take BBT temps, it's unlikely you would miss a pill. It therefore seems to be a bit of overkill to take BBTs while taking the pill.