The 2018 ADA Clinical Practice Recommendations endorse screening Metformin users for vitamin B12 deficiency. In our series, diabetic patients treated by metformin had B12 deficiency in 17% of cases (total B12) and only in 8.5% (HTC). MMA measured with Chromsystems assay.
Please find here publications as guides for reference ranges or therapeutic ranges. As they may differ from other published data. Data vary depending on patient population and measurement method, please determine ranges for your laboratory. When determining ranges make sure that you comply with local national requirements.
Thomas L. (ed)- Labor und Diagnose, 8th edition, TH books (2012)