Also, I should have mentioned most people have better luck with sublingual B12 for quick absorption, though in your case it might not be that important. What is your diet like that you're lacking in B12? Are you a vegetarian?
I wouldn't take GNC brand of anything. I wouldn't buy anything at a GNC. But the best absorbed form of B12 is methylcobalamine, and most supplements are cyanocobalamine. I don't know about the body odor,and the dosage of folic acid seems high, and you're probably leaching out B6 by taking so much of the other two. It could be some additive in the GNC pill, but I don't know.
I've had blood work and I have all the symptoms. 1k mcg of the GNC brand B12. I take 1k mcg of folic acid every other day.
How do you know, and what kind of supplement are you taking?