“Peak, high, and low” results are usually seen with digital OPKs. These can usually either detect different levels of the luteinizing hormone (LH) or measure both LH and estrogen. A "high" result usually happens at the start of the fertile window when there is a rise in estrogen that happens before the rise of LH. Then a "peak" or "positive" result measures the LH surge that suggests you will likely ovulate in the next 24-36 hours and you're at your most fertile. “Positive and negative” results are usally seen on to non-digital OPKs that can only detect if LH is present or not. They are usually positive right before ovulation on your most fertile days.