Metformin is often the first line of drug therapy for many people with Type 2 diabetes, including children.
Unlike the sulfonylureas which act by increasing the release of insulin from the pancreas, metformin doesn't stimulate the pancreas to produce more insulin.
It actually reduces the liver's production of glucose.
Unfortunately, long-term use and large doses of the medication are associated with vitamin B12 deficiency.
Scientists at The Catholic University of Korea in Seoul, Korea, and the University of South Carolina in the United States, compared metformin treatment in combination with other medications to learn which combination would be safer with regard to vitamin B12.
Their study, posted on PLoS One in October 2014, included 394 people diagnosed with Type 2 diabetes...

• a total of 299 participants were treated with metformin and a sulfonylurea while the
• second group of 95 diabetics were treated with metformin and insulin.
  

Although the average B12 levels were normal in both groups, the metformin and sulfonylurea group averaged a lower level...

• the metformin and sulfonylurea group had more cases of vitamin B12 deficiency, with 17.
  4 percent, compared with the
• second group with 4.
  2 percent.
  

From these results it was concluded Type 2 diabetics treated with metformin and a sulfonylurea should be regularly monitored for vitamin B12 levels.
Sulfonylureas work by causing the beta cells in the pancreas to release more insulin.
Examples of this class of anti-diabetic medications include...

• chlorpropamide (Diabinese),
• glimepiride (Amaryl),
• glipizide (Glucotrol, Glucotrol XL),
• glyburide (DiaBeta, Glynase PresTab, Micronase),
• tolazamide, and
• tolbutamide.
  

Vitamin B12 is important for making red blood cells which carry oxygen throughout the whole body.
In a vegan diet, which is said to be the best for Type 2 diabetes, B12 sources include...

• nutritional yeast,
• B12 supplements, and
• supplemented cereal,
• meat substitutes, and
• non-dairy milk (check the label).
  

Nutritional yeast is not used in baking but as flavoring for savory dishes when a cheese flavor is wanted.
BuzzFeed.
com shares 23 recipes using nutritional yeast.
Try a quiche without eggs or cheese.
Or vegan mac and cheese without the cheese.
Anyone for vegan popcorn chicken? Or flavor popcorn with nutritional yeast instead of butter.
Kale chips with nutritional yeast makes a healthful snack.
Some other recipes from BuzzFeed.
com include vegan pasta Alfredo, simple vegan pesto, breakfast nachos, zucchini pizza boats, and more.
Vitamin B12 supplements are also available - with either B12 alone or in combination with other vitamins and minerals.
Mayo Clinic in the United States recommends...

• 2.
  4 mcg of B12 for persons over 14 years of age,
• 2.
  6 mcg for pregnant women, and
• 2.
  8 mcg for breastfeeding women.