For a while I was taking the vitamin B12 supplement. It is recommended particularly for vegans, and often for vegetarians. Even if a person is not vegan or vegetarian they may require supplementation of this vitamin.
Research has shown overall it is better to take a complete B vitamin, or general vitamin supplement. The B vitamins need to work together to function efficiently. See this article for more information: https://www.wellnessresources.com/news/quality-spotlight-compare-b-vitamin-forms