It's good that you keep the temps on 2 different charts because you are right, your temps will be different. So many things can influence your BBT, this is why you have to take your temp at the same time. Your temp at 5 am is likely the most accurate so I'd stick with that. The temp taken at 8 pm has a lot of factors that could influence it. Things like how deep of a sleep was achieved between 5 and 8, did you toss and turn, did you wake up slowly 1 day and abruptly the next, did you take a sip of water when you were up at 5 am, did you wash your hands with hot/cold water. The 5 am temp was likely taken after many hours of deep restful sleep and you probably wake up rather quickly then.

One thing you may actually find is that although your temps are quite different between 5 and 8 am is that your two charts may actually share a very similar pattern (even if they zig zag a little differently) and will likely detect ovulation to be the same day on each chart. It's just that one chart may have a slightly lower trend and the other may have a slightly higher trend.

When in doubt, I'd stick w/ your 5 am temp

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