Vegetarians are probably quite familiar with vitamin B12, since most vegetarians take a multivitamin supplement daily. Vegans are also likely to be more familiar with vitamin B12 and multivitamins than most other people.
A vitamin B12 deficiency is serious. Common symptoms include fatigue, pale skin, mental confusion paranoia, and respiratory problems. If you have these symptoms, see a doctor immediately. There are other reasons for these symptoms beside a vitamin B12 deficiency. If you have one or more of these symptoms and your doctor cannot find a cause, ask about a possible B12 deficiency.
A vitamin B12 deficiency will take years to actually develop. Otherwise healthy vegetarians who do not eat foods that help our bodies create B12 such as dairy products and meats, may not see any symptoms for 10 years or more. Vitamin B12 is not actually in foods, our intestines produce B12 but we need calcium and protein to do so. This is why a multivitamin taken daily is so important. Multivitamins are a preventative measure for most, not a cure for a particular problem. The vitamin B12 found in multivitamins is made from bacteria and the bacteria which is deeply fermented.
No matter if you are a vegetarian or not, a daily multivitamin containing B12 is a good idea. Even people who eat meat may have trouble producing vitamin B12 naturally in their body. Certain antibiotic rich foods like garlic and onions. Even taking oral antibiotics can destroy our bodies ability to produce B12.