h/o (history of)

H&E (hematoxylin and eosin)

H&H (hematocrit and hemoglobin)

H&L (heart and lungs)

H&N (head and neck)

H&P (history and physical)

H+ (hydrogen ion)

H1N1 (Influenza A, swine flu (hemagglutinin type 1 and neuraminidase type 1))

H2 (histamine 2)

H2O (water)