Persistent Fatigue & Tingling Despite Normal B12 Levels Raise concerns About Subtle Deficiency
LONDON – November 18, 2025 02:26:30 GMT – Individuals experiencing ongoing fatigue, numbness, or tingling in hands and feet, even after blood tests indicate normal vitamin B12 levels, may be facing a more nuanced deficiency that standard testing often misses. Experts are increasingly recognizing that conventional B12 assessments may not capture the full picture of B12 status, leaving a significant number of patients undiagnosed and untreated.
While a definitive B12 deficiency is typically identified through serum B12 testing, emerging research highlights the importance of evaluating other biomarkers – such as methylmalonic acid (MMA) and homocysteine – to detect functional B12 deficiency. These tests can reveal whether the body is effectively using the B12 it has, even if levels appear adequate in a standard blood test. An estimated 1.5% to 15% of adults over 50 experience B12 deficiency, with rates increasing with age, but subtle deficiencies impacting quality of life may be far more prevalent.
B12 is crucial for nerve function, DNA synthesis, and red blood cell production. symptoms of deficiency can range from subtle fatigue and weakness to more severe neurological problems. factors that can interfere with B12 absorption include certain medications (like proton pump inhibitors and metformin),gastrointestinal disorders (such as Crohn’s disease and celiac disease),and dietary choices (particularly in strict vegans and vegetarians).
“We’re seeing more and more patients who fall into a gray area,” explains Dr. Eleanor Davies, a neurologist specializing in vitamin deficiencies at St. Bartholomew’s Hospital in London. ”Their standard B12 tests come back within the normal range, but they continue to experience debilitating symptoms. This suggests that the B12 isn’t being properly utilized by the body, and further examination is needed.”
Individuals experiencing persistent symptoms despite normal B12 levels should consult their physician to discuss additional testing and potential treatment options, which may include B12 injections or high-dose oral supplementation. early diagnosis and intervention are critical to prevent irreversible neurological damage. Researchers are currently investigating more sensitive and comprehensive methods for assessing B12 status to improve diagnostic accuracy and patient care.
