Hair transplant after gastric sleeve?

It is best to discuss your medical issues or surgical history directly with your surgeon since each doctor may have a slightly different opinion.

there is no problem in doing your hair transplant 2 month post op. But after gastric operation these vitamins are most likely missing in your body, which can lead to hair loss. Vitamin B, iron Fe, Zinc and folic asid can be low in your blood at this moment. You should take this vitamins before your surgery. 

It should be okay, since they are two completely different procedures. But the two people you should really be asking about this are the surgeon who performed your first surgery and the one who will be performing your transplant, as they each know the specifics of your case and if there are any unusual factors that may require you to wait longer.

Both the stress of surgeries and in particular weight loss surgery will cause hair loss of your natural hair but it should not impact the transplanted hair