What happens if vitamin B12 deficiency is not treated?

Vitamin B12 supports healthy red blood cells and the nervous system. A continuing deficiency may cause fatigue, pale skin, dizziness or generalised weakness as anaemia develops. Nerve involvement can cause numbness and tingling, unsteady walking or reduced strength. Some people also notice memory problems, difficulty concentrating or changes in mood. Nerve symptoms can continue even when anaemia is not obvious, so a normal-looking level of energy does not rule out a problem.

The outcome depends on the cause, how long the deficiency has been present and whether nerve symptoms have started. Prompt treatment may improve blood-related symptoms first; nerve recovery can take longer and may be incomplete when treatment is delayed.

Arrange a medical assessment if symptoms persist or you have been told that your B12 level is low. A blood test can assess blood-cell changes and B12 status, while the clinician reviews diet, absorption problems, medicines and previous surgery. Treatment may involve tablets or injections depending on the cause and severity; do not choose a high-dose supplement without advice, because the cause still needs attention.

Seek urgent medical help for new difficulty walking, marked weakness, confusion, fainting, chest discomfort, breathlessness at rest or rapidly worsening numbness. These symptoms need assessment because severe anaemia or nervous-system involvement can require prompt treatment. For milder fatigue, dizziness, memory changes or tingling, book a timely appointment rather than waiting for symptoms to resolve.

Ask what may be causing the deficiency, whether your blood count and nerve symptoms need review, and whether tablets or injections are appropriate. Ask when improvement should be assessed and which symptoms should prompt an earlier review.