welcome to hcm
thanks for the query
yes iron can cause gastric upset. what is your hb level?
you have to adjust your iron intake according to the hemoglobin
have you informed your doctor about your blood sugar level before starting humira?
are you feeling very tired, poor appetite
if yes then go for a liver
function test. also serum lipid profile
or liver problem can cause such pain under rib cage
if you notice any deviation from normal range in report consult your doctor .
hope this information will helpful to you
wish you good health