I am only on CD 5 so I was not really expecting to see a surge for a bit (my periods are only 3-4 days) but I used a Target Up & Up brand OPK test strip (like the Wondfo style, the little thin ones you dip in urine), and it says to use first morning urine (which is odd, I have always been under the understanding that you use in the afternoon after a 2 hour hold, but I decided I would follow the instructions since last night when I used it the control line was super faint). It also says read it in 4 minutes, but NOT after 5. It looked really faint (test and control line both) when I read it, and I didn't really like that but left it out for a few minutes. It must have been around 10 minutes after taking it and it looks like I would expect it to look when you read it, as in the control line is nice and dark, but the test line is also dark, though not dark enough to consider positive but dark enough for me to think it might be positive very soon. Would you consider that an almost positive and test later, or stick with what it looks like (super faint and hard to read) in the 4 minute time frame? I don't think I'll use these again, I only picked them up because they were a decent deal at 20 sticks for $15 and I didn't think Wondfos would get here in time.