as well as Magnesium could help. If your urine is yellow, you need to drink water until it gets pale. I was on Metformin for years and my b-12 was on the floor at 119. 400 is low end of acceptable, 900+ is where you want to be. Metformin users may have to supplement b-12 as long as they take the medication. I don't know the science of absorbsion but I always get the b-12 that is "Methyl" in the name. I took monthly shots also to boost the numbers. Good Luck, Ken in Texas. P.S. You need to stop supplementation about a week in advance of testing your numbers no matter what you are supplementing.