I've been premenopausal for over 2 yrs now with night sweats like crazy sometimes (I'm under 40). My doc said that it won't show up on a blood test until your cycle completely stops. I can sometimes go 3 months without a cycle. My sisters mate is also perimenopausal and has been since she was 25. So, age doesn't matter. And, the blood test will come back normal if you're having any kind of cycle. I just have my favorite shirts that soak up the sweat and don't make me worse. No tshirts with transfers on them, and some night shirts are out. My husband will have 3 blankets on him and I have a sheet and a fan blowing right on me. I've found on nights that my feet are cold, I have worse night sweats. I also have hot flashes that last minutes not seconds like my mother's. So, menopause is not just a switch that turns off, it can come in many stages and phases and last many years. From what my doc said there really is no test for perimenopause other than the symptoms. Only individuals know if night sweats may be due to their meds or peri/menopause. This is just what I was told years ago.