I’m 19, 5’7, weigh 155 lbs, and wear a 34D. Am I a good candidate for breast reduction?

Hi, thank you for your question. It is difficult to say whether you are a good candidate for a Breast Reduction without photos or a physical exam. Typically, the presence of heavy breasts that causes symptoms in the upper back & neck or rashes under the breasts would warrant a reduction. Consult with a board certified plastic surgeon to review your options. I hope this helps. Best of luck! 

Hello and thank you for your question.
The best thing to do is to schedule a consultation with a board certified plastic surgeon to discuss your options. Best of luck!

You need to determine if the back aches are the result of the size of your breasts.  The best way to determine what your breast size should be with respect to your anatomy and give true advice would be an in-person exam with a board certified plastic surgeon who performs hundreds of breast procedures annually. 
Not only does proportion depend upon the aesthetic balance of your breasts with your shoulders, waist, hips, and buttocks, but also upon your objectives, active lifestyle, soft tissue quality, muscular anatomy, and long-term concerns. There is also a limit to how small you can go due to tissue that needs to be retained for the nipple/areola to maintain a good blood and sensory nerve supply.
No direct correlation exists with cup sizes. A PS cannot guarantee that a breast will be a specific cup size after reduction.  Very large breasts rarely are reduced by more than two or three "cup" sizes.

Without photos or an exam, I can only speak in generalities.  It all depends on how comfortable you are with your present breast size and shape.  If you would like to be smaller and lighter, so there would be less weight and bulk up top, then a reduction will be appropriate.  Whatever weight is removed will reduce the strain on your shoulder, chest, and back.  However, with "only" a D cup and not larger, the amount of breast tissue removed (which depends on your desired final size) may not be enough to make a significant change in any back symptoms.  But I would expect at least a moderate symptom improvement.

Hi.  If you are larger breasted then you would like to be and are otherwise healthy then you would likely be a good candidate for breast reduction.  Of course, you need an in person evaluation.  I would recommend consulting with a board certified plastic surgeon with good experience with breast reduction to be able to examine you and go over the specifics and the options with you.  I have included a link to some typical before and after photos if that is helpful.  Good luck and take care, Dr. Howell