If you're taking Metformin -- an oral medication used to treat type 2 diabetes also known by its brand names Fortamet, Glucophage, Glumteza, Glucophage XR, Riomet and Avandamet -- you might want to consider checking your B12 levels.
A four-year study of 390 patients with type 2 diabetes at Maastricht University Medical Center in the Netherlands found that those taking the drug had a 19% reduction of vitamin B12 levels over time, while those given the placebo showed no notable change in B12 levels.
Vitamin B12, which is essential for neurological function and red blood cell formation, among other things, occurs naturally in many foods and can also be taken in pill form. Symptoms of a B12 deficiency include weakness, fatigue, loss of appetite, constipation, and neurological changes like numbness in the hands and feet.

I’m guessing that means it would be advisable to take a B12 supplement to ensure you’re getting your required daily B12 allowance?