Does the urinary MMA test still reflect a B12 deficiency after a person has been supplementing mB12 for 10 days? I have a friend that appears to me to have CFS and a lot of B12 deficiency symptoms. I suggested that before she added in mB12 and Metafolin supplementation, she should get a urinary MMA test to try to get confirmation that my hypothesis is correct. One week ago she did submit a urine sample for a MMA test. She had no bloodwork done. Since then, she added in daily 1000mcg Jarrow mB12 under the upper lip for 45 minutes, and Pure Encapsulations B Complex Plus, which has 400 mcg Metafolin. She continued on with her usual Vit. D, Omega 3, mag/calcium, and IntraMax supplements. Today she got her MMA results. Apparently the local hospital sent the sample on to Mayo Clinic. It was reported as serum MMA 5.08 nmol/ml, with a ref. range of 0-.4 nmol/ml. When she questioned the local hospital as to why a serum result was given, with serum ref. range and units of measurement, when it was a urine sample, they said they would check into it. Apparently when blood is spun down, the serum looks like urine, so the hospital spokesperson speculated that at some point some tech must have thought they were working with a blood sample. It seems she will have to redo the test. My question is, now that she will have taken mB12 and methylfolate for around 10 days, if my friend had a deficiency before starting mB12 & L-5-MTHF, will the urinary MMA result obtained from a current urine sample still be reflective of a B12 deficiency? How quickly does MMA change when supplementation has been started?