Make sure your doctor tests your B12 levels when you get your blood work done. It is very important.

Vitamin B12 is a water soluble vitamin that is essential for functioning of the brain. It effects depression, mood, fatigue, neurodegenerative disorders and is implicated in many diseases such as mental illness, multiple sclerosis and cardiovascular disease.

Vitamin B12 is only produced through bacterial fermentation in animals. No plant source creates B12. So as a nutritional guide to increase your B12 intake one must look to increasing B12 by eating animal products such as meat, dairy and eggs.

Vitamin B12 is supplemented in many food products, however large number of individuals have problems with absorption through the gut of vitamin B12. In this case it is necessary, and common, to get B12 shots or nasal sprays to compensate. If your B12 levels are low you should ask your doctor about how to properly supplement your intake.

Symptoms of B12 deficiency may include:

loss of muscle strength

Fatigue Memory loss or "Brain Fog"

Pale skin

Anxiety/Depression

Read more here: https://chriskresser.com/b12-deficiency-a-silent-epidemic-with-serious-consequences/