Do I need to lose weight to be eligible for breast reduction? I’m currently a 42L and 310 lbs.

None of us can predict what decisions insurance companies will make regarding coverage for BR surgery or what documentation will sway their decision. BRs which are medically necessary (i.e. you suffer back, shoulder, and neck "pain" with DOCUMENTED medical attention over a period of a YEAR) are typically covered by medical insurance. If not, your medical insurance may try to deny you based upon a lot of things such as weight, lack of symptoms, lack of previous medical management, and lack of enough tissue that should be removed.
Read your medical insurance certificate of coverage. Determine what medical information is required for your medical insurance company to issue a pre-authorization or predetermination of benefits for BR surgery. Then seek consultation with a board certified plastic surgeon who can evaluate your medical condition, discuss the pros and cons of this surgery as it applies to you, determine the amount of tissue to be removed, and help you in completing the paperwork required by your medical insurance company. (Take all documentation you have accumulated to your board certified PS's consultation appointment.)

Dear Starheart,
breast reduction is best suited for women who wish to decrease the size of their breasts. While there are different techniques used to perform this surgery, I prefer the vertical incision (lollipop pattern) breast reduction technique instead of the anchor scar pattern, which reduces more noticeable scarring than usual. I also use a SAFE liposuction technique to reduce additional fat around the stubborn axilla area and bra line. This way, my patients are achieving beautiful results with minimal incisions which reduces downtime and delivers an overall better breast shape long term.If you are considering breast reduction surgery, you should consult with a board certified plastic surgeon to discuss your options and make sure your surgeon understands your goals. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery