“Because the body can store B12 for three to five years, early symptoms of a deficiency usually appear gradually, so you’re unlikely to notice them,” says Middleberg. After initial clues like fatigue, weakness, and brain fog set in, says Middleberg, more advanced tip-offs show up, such as numbness and tingling of the limbs, depression, and paranoia, even hallucinations. The signs are so varied and they don’t strike everyone, so it’s tough to diagnose even at a later stage. “Which symptoms hit when depends also on what caused the deficiency—malabsorption, which could mean they are absorbing some B12 and the deficiency is occurring more slowly, or total lack of animal products, which would likely cause the deficiency to develop more quickly,” says Middleberg.
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