TTC - estradiol levels very low, everything else fine

[crazycatmummy]

Hi.
I recently had my blood test results which showed that my e2 (estradiol) levels were very low, he compared it to being as low as after menapause. This test was done one day 2 of my cycle. He's requested that I get a second blood test done between days 5-7, I'm unsure of which day I should go?
Has anyone had the same issue? Or does anyone know which day would be best to get peak results? My cycle is on average 30 days. If it comes back low again he's going to refer me to a horome specialist.
Thanks.