What causes generalised weakness?

Generalised weakness means reduced strength or energy across the body, rather than weakness confined to one arm, leg, or side. Dehydration may cause thirst, dry mouth, dizziness, and reduced urine. Hypoglycaemia can bring sweating, shaking, hunger, confusion, or weakness, particularly in someone using diabetes medicines. Anaemia, iron deficiency anaemia, or vitamin B12 deficiency may cause tiredness, breathlessness on effort, paleness, numbness, or concentration changes.

An underactive thyroid can be associated with feeling slowed down, cold intolerance, constipation, dry skin, or weight change. Type 2 diabetes may cause thirst and frequent urination, while infection can cause fever and marked loss of strength. Sudden weakness on one side, facial drooping, speech trouble, or new difficulty walking is a different emergency pattern.

Sit or lie down if unsteady, take fluids if you can, and eat a regular meal unless a clinician has given different instructions. Review any recent illness, heat exposure, bleeding, diet change, or new medicine. Do not stop prescribed treatment without advice. A clinician may check your strength, blood pressure, blood sugar, blood count, vitamin levels, and thyroid function according to your symptoms.

Call emergency services for sudden one-sided weakness, facial drooping, speech difficulty, severe confusion, collapse, chest pain, severe breathlessness, or inability to stay awake. Seek urgent assessment for weakness with high fever, rapid deterioration, very little urine, persistent vomiting, or signs of sepsis such as feeling profoundly unwell with fast breathing or a racing heartbeat. Arrange a routine appointment when weakness persists, recurs, or limits ordinary activities.

Ask which causes fit your accompanying symptoms, what tests are appropriate, whether any medicine needs review, and how to stay safe while your strength is reduced.