Feeling tired all the time? You might have a Vitamin B12 deficiency — Here are the warning signs

Vitamin B12 is an essential nutrient which isn't just for energy; it is important for proper nerve function, red blood-cell production, and overall brain health. However, this deficiency often goes unnoticed in many people as their signs and symptoms are subtle and so, they are often overlooked as “just stress” or “lack of sleep.” According to a 2015 study titled 'Vitamin B12 deficiency – A 21st century perspective' people without obvious anemia can have low B12 levels that lead to nerve damage, mood changes, or cognitive issues (in the long run).
This makes recognising Vitamin B12 deficiency warning signs early on important to prevent any long-term damage. So, here we list some early warning signs one should not miss:

One of the classic signs of Vitamin B12 deficiency is persistently feeling drained or lack of energy. When B12 is low, red blood-cell production drops-- this impairs the body’s ability to carry oxygen, leading to lethargy and dropping stamina. As per the 2015 study 'Vitamin B12 deficiency – A 21st century perspective' , neurological symptoms can show up even without anemia, which means you could be tired for reasons you don’t readily suspect. So, if you constantly feel tired despite proper diet and rest, then it could be a sign of B12 deficiency.

Another common sign of Vitamin B12 deficiency is tingling or numbness in your hands or feet. Why? Well, low Vitamin B12 can damage the protective covering of nerves (called the myelin sheath), thus resulting in those odd sensations. If ignored for too long, it can cause major nerve damage. And so, it’s important not to dismiss numbness or burning sensations.

Have you noticed experiencing memory loss, brain fog, and a lack of focus lately? This could be due to B12 deficiency. A 2025 study by researchers at the University of California, San Francisco (UCSF) found that even older adults with Vitamin B12 levels in the normal range but on the lower side showed slower cognitive processing speeds and changes in brain white matter. These lower but "normal" levels of B12 were linked to subtle cognitive declines, slower visual processing speeds, and greater brain white matter damage.

Low B12 doesn’t just affect your body — it can also affect your mood. Constantly feeling irritable, sad, or anxious may be linked to a Vitamin B12 deficiency affecting your nervous system. A recent review titled 'The association of vitamin deficiency with depression risk,' published in April 2025 in Frontiers in Psychiatry, shows how vitamin deficiencies, including vitamin B12 deficiency, contribute to the risk of depression. It emphasises that low Vitamin B12 is associated with increased depression risk.

When Vitamin B12 is too low, defective red blood cells break down, leading to anemia and symptoms such as pale skin or a yellow tinge (jaundice) and rapid heartbeat, as per the National Health Services.

However, these symptoms often overlap with other health conditions, they can easily be overlooked. If you notice two or more of the above signs, then do get your Vitamin B12 levels tested and consult a doctor.
Disclaimer​
The information presented in this article has been compiled from multiple media and research sources. This content is intended for general awareness and should not be taken as medical advice or a definitive scientific conclusion.