Do I need to supplement vitamin B12?

It is recommended that most adults take a 500 mcg sublingual daily, or take 1,000 mcg swallowed, to ensure that they don't develop a vitamin B12 deficiency. Nutritional yeast and enriched non-dairy milks do have B12, but the amount may not be sufficient for those with absorption issues, or for those over age 50, or for those who use caffeine, alcohol, or vinegars. Most of us probably should supplement in addition to our multivitamin. Don't worry about taking too high a dose of B12. Any excess will be excreted through your urine. Vitamin B12 can be excessively excreted through urine in people who use caffeine, alcohol, or vinegars. These liquids may act as a mild diuretic, causing us to excrete nutrients in urine.

A B12 deficiency can lead to serious issues including anemia or nerve damage with the following symptoms: weakness, tiredness, light-headedness, rapid heartbeat and breathing, pale skin, sore tongue, easy bruising or bleeding, stomach upset, weight loss, and diarrhea or constipation. and nerve damage, numbness, mood changes, and memory loss.

Hydroxycobalamine has not been shown to break down to tiny amounts of cyanide in the body, which could happen when the common form of vitamin B12 is taken as cyanocobalamine. The clinical significance of tiny amounts of cyanide in the body is not completely understood.

Problems are more likely when vitamin B12 blood levels are below 400, but less than 1% of patients have symptoms of clinical significance when levels are above 400.

A physician can order a vitamin B12 level, which is usally not that expensive, each year as one ages, if a person has not been taking a supplemental vitamin B12 regularly. The more somebody complains of fatigue or depression or anxiety, the more the physician might consider testing for occult B12 deficiency.