Thank you for your question.
The best person to discuss this with would be your plastic surgeon seeing as every surgeon may have a slightly different protocol. Common causes of low hemoglobin levels are due to deficiencies in iron, vitamin C and B12 so I would recommend including these supplements in your diet. I would also eat iron and vitamin C rich foods such as red meat, spinach, almonds, oranges, strawberries and broccoli. This should help raise your hemoglobin levels. Best of luck!
James Fernau, MD, FACS
Board Certified ENT
Board Certified Plastic Surgery
Member of ASPS, ASAPS, ISAPS, The Rhinoplasty Society, AAFPRS, OTO/HNS, ASLMS, International Federation for Adipose Therapeutics & Science