Too much vitamin b12 side effects

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Vitamin B12 is a common vitamin supplement administered orally or through injections. It's normally harmless, but too much B12 can have negative side effects.


Vitamin B12 is a water-soluble vitamin that's important in the production of red blood cells and nerve cells. It's absorbed into the bloodstream during digestion. Foods such as shellfish and meat are good sources of the vitamin.

Primary Side Effects

The primary physical side effects of taking too much B12 include mild diarrhoea, skin rashes, hives, breathing problems and heart palpitations. Symptoms are typically mild and disappear within 24 hours after ingestion. The side effects are more common when the vitamin is administered through injection.

Secondary Side Effects

Vitamin B12 can have negative psychological side effects. They include panic, anxiety attacks and insomnia. These side effects can lead to breathing problems and heart palpitations created by panic and anxiety. The symptoms typically disappear within a few hours, as the excess B12 is flushed from the system.

Rare Side Effects

People considering B12 supplements should consult their family medical history for any occurrence of Leber's disease, a hereditary condition that causes the optic nerve to atrophy. Large doses of B12 can lead to an early onset of the disease or cause the optic nerve to atrophy more rapidly.

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