I often get conflicting findings when I order serum MMA, B12, homocysteine and CBC MCV. Can you help me understand what to do when MMA is low and other markers are higher, vice versa?

Chris Kresser:  Yeah, so good, that’s par for the course. I also get conflicting markers there. I don’t know that I would say they’re conflicting. I would say that serum MMA seems to be less sensitive as a marker of B12 deficiency than urine MMA is. So I more regularly see elevated urine MMA and when homocysteine is high, then I do serum MMA. And serum MMF, remember, is affected by SIBO. It’s not as reliable with bacterial overgrowth. So and a lot of patients have that, so that’s something to consider. Whereas urine MMA is not as accurate when you have patients with diabetes or kidney problems. So if I had to pick between those, I would definitely pick urine MMA. But homocysteine itself is a pretty sensitive marker. So if you see homocysteine high and urine MMA is maybe high-normal, and serum MMA is normal, I would still be, I would question B12 deficiency. But if the MMAs are normal and B12 is normal and homocysteine is high, then you’re almost certainly looking at folate deficiency. So that’s where you look at formiminoglutamic acid, or FIGLU, if you’re doing the full urine organic acids, or you could and you’re looking at serum folate, possibly red blood cell folate, although that’s more of a marker of long-term folate status than recent intake, and then you’re looking at possibly like a methylation panel like from HDRI, Health Diagnostics and Research Institute, that looks at all of the folates individually. So hopefully that helps. Low MMA, I’m not sure if that has any clinical significance. I assume you’re talking about serum, or serum or urine. I don’t know that that has any clinical significance.