Q: When is ovulation and BBT rise after a positive OPK?
A: Your first OPK indicates a rise in the LH hormone, which is followed soon after by ovulation, which is triggered by that LH rise. It is essential that this is the first positive OPK. This means you must have a negative OPK followed by a positive OPK. Just having one positive OPK test without a preceding negative test does not provide enough information, as the OPK can be positive for 2-3 days.
Usually, you would expect to ovulate about 14-26 hours after the OPK FIRST becomes positive (a positive test after a negative test). However, it can occasionally happen that you have already ovulated even before your OPK first becomes positive. By taking the OPK more frequently than every 24 hours, you may be able to pinpoint ovulation better. Your BBT curve should go up within 24-48 hours after ovulation.
Sometimes, especially with a slow rise, it can take up to four to five days to see the BBT rise after the OPK first becomes positive, but ideally, you see the rise within two to three days.