By: Kacie Shrock, RN, BSN | November 14, 2022
If you are trying to conceive, you are probably very familiar with the fertile window and how chances of conception increase as you approach ovulation day. LH (Luteinizing Hormone) tests, also known as ovulation tests or OPKs, are a vital tool for trying to get pregnant. They can help identify your most fertile days of the cycle with accuracy to time intercourse accordingly and increase your chances of conception.
LH Surge v. LH Peak: What are they?
LH is the hormone in the body that surges once per month and is responsible for triggering ovulation aka the release of an egg. The LH surge signals the beginning of the rise in LH or opening of your fertile window, which can last anywhere from a few hours to a few days and is detected by using ovulation tests. The LH peak occurs on only one day each cycle. Your peak is the last, highest result of luteinizing hormone during your cycle.
How long after LH surge do you ovulate?
Ovulation is a science so there is no cut and dry answer on when ovulation will occur after a surge or peak, but rather a range of possibilities. As ovulation approaches, the ovaries release estrogen which sends a message to the brain to release that surge of luteinizing hormone. High levels of luteinizing hormone is what triggers ovulation which happens about 28-36 hours after the beginning of the LH surge, or 8-20 hours after the true LH peak.
Looking at the chart above you can see an LH surge on CD 25, with ovulation happening on CD 26 that was confirmed by a rise in BBT on CD 27.
How can I find my LH surge?
By using ovulation tests, you can catch the timing that LH levels begin to rise and also identify when they reach a peak level. You will want to start using LH testing kits the day after your period ends up until you have confirmed ovulation, or 2-3 days after your detected peak.
You can test once per day between the hours of 10am-8pm after your period ends, and increase your testing to twice per day during your predicted fertile window to ensure you don’t miss that peak. It is recommended to continue LH tracking for 2-3 days after your LH peak to ensure you have truly identified your peak. You may also stop tracking when your BBT (basal body temperature) reading spikes confirming ovulation occurred, whichever method of tracking suits your needs.
If you have not found your LH surge, or are having low LH levels, keep testing! It is possible that ovulation just hasn’t happened yet and does not mean that you are having an anovulatory cycle. The follicular phase of the cycle can vary, meaning ovulation can fluctuate a little month to month, so if ovulation is a little delayed this cycle, don’t give up just yet!
When should I time sex around my LH surge?
Since the fertile window is 6 days long including ovulation day, you want to start timing sex a few days before you ovulate to ensure the sperm are waiting in the fallopian tubes ready for that perfect egg to be released.
Because there is a range of when ovulation can happen after the start of an LH surge and the sperm can survive up to 5 days, it’s important to have sex the days leading up to ovulation, on your LH surge and the following 1-2 days. The Premom app is a great tool to help you visualize and easily plan out what days to have sex to best increase your pregnancy chances.
Kacie Shrock is a registered nurse who specializes in fertility and reproductive health. She has always had a passion for women's health and she supports women and couples virtually across the world while on their journey to their dream families!
PubMed. National Center for Biotechnology Information. https://pubmed.ncbi.nlm.nih.gov/.
J; K. Ovulation detection in the human. Clinical reproduction and fertility. https://pubmed.ncbi.nlm.nih.gov/6821195/