Medical Term Definition
Weakness
A reduction in the ability to generate normal muscle force or perform physical activity effectively.
True muscle weakness means reduced strength and can result from problems affecting muscles, nerves, the brain, spinal cord, or other body systems. It can be localized to one part of the body or generalized.
People sometimes use “weakness” to describe fatigue, tiredness, or lack of energy, but these are not necessarily the same as objectively reduced muscle strength.
QUICK FACT
Weakness is not the same as fatigue. A person can feel exhausted without having reduced muscle strength, while true weakness can occur even without feeling particularly tired.
COMMONLY CONFUSED WITH
Fatigue: a feeling of exhaustion or reduced energy or endurance; weakness specifically concerns reduced ability to generate force.
SEE ALSO
Clinical & Educational Context
Discussed in Health Articles & Guides
Explore how "Weakness" is covered across our evidence-based editorial guides:
4 Articles
Health in the Wild
If someone develops neurological symptoms such as blurred or double vision, difficulty swallowing, difficulty speaking, weakness, or breathing difficulty after eating potentially contaminated food,...
The Hard Parts of Medicine
Persistent tiredness, recurrent infections, or unexplained weakness deserves appropriate assessment rather than repeated trials of different supplements.
The Hard Parts of Medicine
Falls and loss of independence
Some medicines can cause dizziness, low blood pressure, drowsiness, impaired coordination, or muscle weakness.
Cases & Narratives
Seek urgent medical care if someone with suspected or confirmed malaria develops worsening symptoms, confusion, unusual drowsiness, difficulty breathing, repeated vomiting, inability to drink...
