Low B12 and Low Methylmalonic acid

I have been having extreme daytime sleepiness and had a sleep study and MSLT. I passed the MSLT for narcolepsy and was given Ritalin. I had my doctor check to see if it could be a B12 deficiency. My B12 level came back 150. He then ordered me a methylmanic acid test to see if it is an actual deficiency. That result came back a little low as well. It was 81. When I asked him about it, he mostly said that he just didnt know what that combo meant. I tried looking online and cannot find that combonation and what it means. Any info would be great- thanks

[Renee Radenberg]

Methylmalonic acid (MMA) is a by-product when proteins (amino acids) in the body break down.  This test measures the amount of methylmalonic acid in your blood. MMA is not routinely ordered by doctors. Sometimes if the vitamin B12 is the lower portion of the normal range, it may be ordered along with homocysteine test. If MMA and homocysteine levels are elevated and vitamin B12 are mildly decreased, then early or mild vitamin B12 deficiency may be occurring. If MMA and homocysteine levels are normal, then a deficiency of vitamin B12 is unlikely. Decreased MMA levels are not clinically significant because it is the elevated levels that prompt suspected vitamin B12 deficiency.