Originally Posted by mrsD

B12 does not typically upset the GI tract. The amount in each tablet is quite minute. It is not even absorbed very well, so you should take it on an empty stomach, and choose the activated form called methylcobalamin or methylB12 for short.

Iron is a different thing altogether. Iron really should be supervised by a doctor. How long to take it, how much, etc. Taking iron when you don't need it, can lead to toxicity as it is stored in organs and over time poisons them. Iron is not well absorbed, and much remains in the GI tract and comes out in the stool. The body does not want to easily absorb it, because it of its potential toxicity. You should have bloods tests done to show when your anemia has improved enough to cut back on it finally.