What Is a Functional Vitamin B Deficiency?
                                
                                
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                                    5 min read                                
                            
                                According to the National Institutes of Health, up to 40% of older individuals may have low serum vitamin B12 but normal metabolic status. This illustrates a key aspect of what is a functional vitamin B deficiency, a condition where the body cannot effectively utilize B vitamins, even when standard blood tests appear normal.