Why do i have a 40 to 45 day menstrual cycle i am nearly 39 is this normal?

Yes: It is normal for some women. For more information click here --> http://www.mayoclinic.org/diseases-conditions/perimenopause/basics/definition/con-20029473

Long: Is this a change in your cycle length? Menstrual cycle is usually about 21 to 35 days in women. It is usually around 21 to 45 days in younger teens. If you are experiencing menstrual cycle changes would check with your gynecologist. Take care.