It is alright if you miss a day or two of measuring.
With that said, you should always aim to measure as often as possible, especially if you just got started with Natural Cycles, to get the best results.
The more data you enter in the app, the better the algorithm gets to know you and your unique cycles.
With less data, the app may give more red days as a precaution, but this will even out once you start adding data regularly again.
You should exclude your temperatures if:
- You have slept 2h+ more/less than usual
- You have already snoozed your alarm
- You have slept very poorly, or been awake in the last 4h
- You have had more than 2 alcoholic beverages the night before
- You have already gotten out of bed
- You feel sick