Which of the following is a common cause of B12 deficiency?

Vitamin B12 deficiency is often caused by factors that impair absorption or increase utilization or requirement of the vitamin. One of the common causes is related to the use of Metformin, a medication commonly prescribed for type 2 diabetes. Metformin can interfere with the absorption of vitamin B12 in the intestines, leading to a deficiency over time if not monitored appropriately. The mechanism may involve changes in gut motility and the effect of the drug on the intestinal microbiome.

In contrast, while iron deficiency and chronic inflammation generally lead to other types of anemia, they are not direct causes of B12 deficiency. NSAIDs, while they can cause gastrointestinal issues and potentially lead to malabsorption, are not specifically linked to the impairment of B12 absorption. Thus, the relationship between Metformin and B12 deficiency makes it the most relevant and recognized cause among the options provided.