Malabsorbtion is always a factor. I wouldn't worry about taking them both together because A) B vits are water soluble, and wasted in the urine if you take too much and B) the iron in Floradix is ferrous gluconate, which has a poor absorbtion rate (so you're not absorbing all you take). I had good results with Floradix, and Florvital after we went gf, even if they are poorly absorbed. If you get constipated, then start thinking you're taking to much. Other things to think about- Vitamin A status is related to your ability to absorb iron (natural vitamin a from fish oil will help, not the synthetic palmitates) and we need way more than the RDA. Taking c with your iron aids absorbtion (this is why floradix worked for me i think). Also, tea inhibits iron absorbtion- i can't remember the mechanism (tannins come to mind). so if you're a big tea drinker, back off. I wouldn't count on the gluten tests- the real test is avoidance.