What size breasts do yo uhave to have to qualify for a breast reduction?

Not So much a size..: It's not so much the size as it is the symptoms. Size combined with the symptoms of back, neck, and shoulder pain indicate the need for a reduction.

It depends: Breast reduction surgery may occasionally be covered by medical insurance if there is a medical necessity that can be proven and documented. This requires symptoms of neck/back pain, severe rash and large enough breasts to likely be responsible for the symptoms. There is a scale (the schnur scale) used by some insurance companies to correlate the size with the body habitus.

No Specific Size: There are no specific size breasts that “qualify” for breast reduction surgery. Much will depend on the relative size of the patient's breasts to the remainder of her torso. Disproportionately large breasts tend to be symptomatic. Insurance companies will often evaluate breast size, patient body weight, symptoms, other “modalities” of treatment tried etc. When making determinations eligibility.