Vitamin deficiency and tiredness: what to know

Low levels of nutrients involved in red blood cell production or energy metabolism can leave you feeling drained, weak, light-headed or less able to concentrate. Iron deficiency and anaemia are common considerations, while vitamin B12 or folate deficiency may also be relevant. Poor intake, restricted diets, absorption problems such as coeliac disease, alcohol use, or ongoing illness can affect nutritional status. Tiredness alone cannot identify which nutrient is involved.

A clinician may ask about food intake, menstrual or other blood loss, bowel symptoms, medicines, sleep and mood. Blood tests can help distinguish a deficiency from thyroid, kidney, infectious, psychological or sleep-related causes.

Arrange a medical review if tiredness persists, affects work or daily activities, or comes with breathlessness, paleness, numbness, weight change or bowel symptoms. Bring a list of medicines and supplements and describe your usual diet. Do not start high-dose vitamins simply because you feel tired: the right test and dose depend on the suspected deficiency, and some supplements can mask another problem or interact with treatment.

Regular meals, adequate fluids, a varied diet and a consistent sleep routine can support energy while you seek advice. A clinician may recommend treating an identified deficiency and checking whether symptoms improve.

Seek urgent help for severe breathlessness, chest pain, fainting, new confusion, marked weakness, black or bloody stools, or rapidly worsening symptoms. These signs can reflect a problem that needs prompt assessment rather than self-treatment with vitamins.

Ask which causes of tiredness fit your symptoms, whether blood tests are appropriate, whether your diet or digestion could affect absorption, and how long any recommended supplement should be taken.