My breast size is 36 I want them 28 what should I do without surgery

NOT possible without MAJOR surgery.

First, 38 is the measurement of your chest. This includes your back and sides. If you measure just under your breasts, that would give you an idea of your body measurement. It might be that even totally flat chested you could be more than 28.

Breasts are measured by cup size. So you could be a 36A which means small breasts but a large torso.

But the bottom line here is that the ONLY way to reduce the size of your breasts is via surgery.

I have to add to the comments. Scott is right. With having big boobs (32F!), I'm often at Bravissimo getting measured and trying the specialist bras, so I know a bit. A lot of the time, if the first (The number) size is large, it could mean you're overweight. Because it measures round underneath your boobs and round your back. May I ask your weight and height? If you're perfectly healthy, and not overweight, then I wouldn't worry, and I'd just enjoy having bigger boobs.

X Dani

Agree, there is no way to go to that size most likely at all, depending on size of frame. But without surgery there is nothing that can be done. And there has to be a reason for surgery as breast size causing health issues.