What does generalised weakness feel like with vitamin B12 deficiency?

The weakness may build gradually. Everyday tasks can take more effort, and you may feel tired after activity that was previously manageable. Vitamin B12 is needed for healthy blood cells and the nervous system, so deficiency can also cause a sore tongue, pale skin, breathlessness on exertion, pins and needles, numbness, balance problems, or a change in memory and concentration.

These symptoms overlap with other conditions. A plant-based diet without supplementation, absorption problems, stomach or bowel disease, and some medicines can increase the chance of deficiency, but only an assessment and appropriate blood tests can confirm the cause.

Book a medical review if weakness persists or occurs with tingling, numbness, balance change, or a sore tongue. Take a list of medicines and supplements, describe your diet, and mention any stomach or bowel symptoms. Do not rely on supplements alone when nerve symptoms are present, because the underlying cause may need treatment.

Seek prompt medical advice for worsening balance, new difficulty walking, marked breathlessness, confusion, or rapidly progressing numbness. Seek emergency help for sudden one-sided weakness, facial drooping, speech difficulty, or collapse, as these can indicate a different urgent problem.

Ask which blood tests are appropriate, whether medicines or absorption affect your B12 level, and whether treatment should be given by mouth or injection. Ask how nerve symptoms will be monitored.