What are appropriate Estrogen levels for first few days of period?

I have been having light, brown spotting with some red here and there. I have been on Metformin for three months now and becoming regulated. I went in for blood work to see if it was start of my menses and the nurse said my estrogen was 52? Is that a good level for a few days into a period? I am not doing a medicated cycle this month, so haven't got much info from the nurse. Thanks!