I am 22 years old. My breast cup size is 36b but my under bust size is 34. Should I get a reduction or is 36b OK for me?

Thank you for your query. Based on your description, you do not appear to be a candidate for breast reduction. You may want some reshaping of the breasts,if you wish, but reduction of a B cup breast is not to be recommended. Please find an experienced Board certified Plastic surgeon who can examine you and help you with all your concerns. All the best !

At size 36 B, it is
very unusual to undergo a breast reduction. 
It is possible you will benefit from a breast lift instead and I
recommend The Bellesoma Method.  This
technique will reshape your breast tissue creating upper pole fullness without
implants, elevate them higher on the chest wall and more medial to increase
your cleavage.  Vertical scars are
avoided, nipple sensation and the ability to breast feed are maintained.  The weight of the breast is transferred to
the underlying pectoralis major muscle resulting in pain relief and long term
stability.  Best Wishes,Gary Horndeski, M.D.

Hi! I would not consider a breast reduction based on your bra size. Things to consider for a breast reduction are: Back pain, grooving, rashes under the breast etc...I would suggest setting up a consult with a board certified plastic surgeon. 

The benefits of a breast reduction include the relief of upper back, lower back, shoulder, and neck pain.  The desired breast size and the breast weight/reduction are factors that best discussed with your surgeon.

As noted below 36 B is fairly small already. A breast reduction would be uncommon in this situation. Are you maybe considering a breast lift? Without more information it is tough to address your concerns directly. Please consider meeting in consultation with a board certified plastic surgeon to discuss your concerns. 

Whether you need or want a breast reduction shouldn't be based on bra size.  Bra sizes are very inconsistent across brands and even within the same brand.  You should only consider having breast reduction surgery if you feel that your breasts are too big for you, or your frame.  Have a chat with your local doctor to further discuss if you are contemplating surgery.  All the best

Thanks for your question, sweety789re.
The answer is entirely up to you. Women get breast reduction surgery because they experience inconveniences because of their big breasts, such as back and neck pain, bra straps digging into the skin, and skin chafing and irritation. If you experience these problems as well, then breast reduction may be for you.
There is also no right size for breast reduction - it depends on what you want. That said, the best thing to do right now is to go to a reputable and board-certified plastic surgeon so that he can personally assess you and give you recommendations on breast reduction surgery.
Good luck!

There is no right size, it is simply whether you are happy with what you have or whether you would rather surgically change your anatomy. If you are not pleased with the current situation, consult with 2-3 experienced surgeons for ideas on altering your anatomy. I cannot imagine any experienced surgeon would consider putting a patient through a breast reduction when they are only a B cup unless there are gender issues.