I had gastric bypass 2 years ago & my hair is very thin. what specific vitamins can i take for hair growth/volume?

Vitamin injections: After gastric bypass your body has a hard time absorbing certain vitamins. Injections bypass this issue so talk to your doctor about injectable vitamins such as b-12 and b-complex.

B vitamins: I expect there are several vitamins that could be affected. The one i would be most concerned about is b12. Deficiency can cause hair loss and other problems. However, you might not be able to get enough by taking it orally. Many people need a monthly injection to maintain a normal B12 level. Adequate protein intake is important for hair also. You can have a blood test to check B12 and other vits.