How can the normal limits of the endometrial thickness be determined when i bleed 25 days a month, (5 mm at age 39)w/ history endometriosis&ovarian cysts?

Evaluation : It is not normal to bleed 25 days a month and the endometrial lining is expected to be thin since you are shedding the lining each time that you bleed. Once your obgyn will determine the underlying cause of your bleeding and your cycles will return to be normal then you can evaluate the thickness of the lining. The best time to evaluate the lining is prior to ovulation.