LOL! PT lasted 3 days... He's now a Pescatarian. What's the frakin point?!

You can get vitamin B12 deficiency if you're a vegan (meaning you don't eat any animal products, including meat, milk, cheese, and eggs) or a vegetarian who doesn't eat enough eggs or dairy products to meet your vitamin B12 needs.
Babies born to mothers who are vegetarians may also not get enough vitamin B12.
Symptoms of Vitamin B12 Deficiency

A deficiency of vitamin B12 can lead to vitamin B12 deficiency anemia. A mild deficiency may cause only mild, if any, symptoms. But if untreated, it may cause symptoms such as:

• Weakness, tiredness, or light-headedness
• Rapid heartbeat and breathing
• Pale skin
• Sore tongue
• Easy bruising or bleeding, including bleeding gums
• Stomach upset and weight loss
• Diarrhea or constipation

Vitamin B12 deficiency treatment depends on the cause.
If pernicious anemia or a problem with absorption is the cause, you'll need to replace vitamin B12, usually by injection, or by prescription.
If the issue is that you don't eat animal products, you can change your diet or take supplements.
For most people, treatment resolves the problem. But any nerve damage that happened due to the deficiency could be permanent.