Medical Author: Melissa Conrad Stöppler, MD
Weakness is a decrease in the strength in one or more muscles. In the strictest sense, the medical definition of weakness refers to loss of muscle strength, and this article is focused upon conditions that can result in a measurable loss of muscle function. Weakness may be generalized or may affect one muscle or muscle group exclusively. Diseases of the neuromuscular system, injuries, metabolic diseases, and toxins can all cause of measurable muscle weakness. Signs and symptoms of weakness can include trouble doing daily tasks, such as grooming or writing or problems with gait and loss of balance.
Many people use the term weakness as a synonym for tiredness, weariness, lack of energy or fatigue, although this is not technically correct. People suffering from certain medical conditions (for example, chronic fatigue, insomnia, cancer, heart disease, adrenal disease, or influenza) may describe feelings of total body weakness, referring to feelings of malaise or tiredness, even though no detectable loss of muscle strength is present.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.
Causes of Weakness
14 Signs and Symptoms of Stroke (FAST)
Stroke is a serious medical condition. If you think you or someone you know is having a stroke call 911 immediately....
Addison disease is a hormonal (endocrine) disorder involving destruction of the adrenal glands (small glands adjacent to the...
ALS (Amyotrophic Lateral Sclerosis) Symptoms, Causes, Life Expectancy
Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease) is a neurological disease that progresses rapidly. The disease attacks...
Amyloidosis is a group of diseases resulting from abnormal deposition of certain proteins (amyloids) in various bodily areas. The...
Ankle pain is commonly due to a sprain or tendinitis. The severity of ankle sprains ranges from mild (which can resolve within...
Are You Too Sick to Work?
When you're not feeling well, it may be difficult to decide whether to stay home or go to school or work. Conditions that are...
Atrial Fibrillation Symptoms (AFib Warning Signs)
Atrial fibrillation or AFib is a type of hear rhythm abnormality. Early warning signs and symptoms of atrial fibrillation...
Atrial Fibrillation vs. Ventricular Fibrillation (AFib vs VFib ECG Strips)
Atrial fibrillation (AFib) and ventricular fibrillation (VFib) are problems with the heart that cause abnormal heart rhythms....
Bell's Palsy (Facial Nerve Problems) Paralysis Causes and Treatments
Bell's palsy is one type of facial nerve paralysis. The 7th cranial nerve controls the muscles of the face, and although...
Botulism is an illness caused by a neurotoxin produced by the bacterium Clostridium botulinum. There are three types of botulism:...
Cancers that form from brain tissue are called primary brain tumors. Brain tumors may be malignant (brain cancer) or benign....
Brain Lesions (Lesions on the Brain)
A brain lesion is defined as an area of damaged brain. Brain lesions (lesions on the brain) are caused by: trauma,...
Carpal Tunnel Syndrome
Carpal tunnel syndrome is a condition in which irritation of the wrist's median nerve causes tingling and numbness of the thumb,...
Cerebral palsy (CP) is an abnormality of motor function and postural tone acquired at an early age (even before birth). Cerebral...
Charcot-Marie-Tooth Disease (CMT)
Charcot-Marie-Tooth disease is one of the most common inherited neurological disorders. Charcot-Marie-Tooth disease affects the...
Chickenpox (chicken pox) is a contagious childhood disease caused by the varicella-zoster virus. Symptoms have an incubation...
Childhood Acute Lymphoblastic Leukemia (ALL)
Childhood acute lymphoblastic leukemia is the most common type of cancer in children. Symptoms and signs include fever, easy...
Cold vs. Flu
Though the common cold and flu share many signs and symptoms, they are caused by different viruses. Signs and symptoms include...
Colon cancer is a malignancy that arises from the inner lining of the colon. Most, if not all, of these cancers develop from...
Concussion is a short-lived loss of brain function that is due to head trauma. There are two types of concussion, simple and...
Connective Tissue Disease
Connective tissue disease is when the body's connective tissues come under attack, possibly becoming injured by inflammation....
Creutzfeldt-Jakob disease (CJD) is a rare, degenerative, invariably fatal brain disorder. CJD generally appears in the later...
Cysticercosis (Pork Tapeworm Infection)
Cysticercosis is an infection caused by Taenia solium, the pork tapeworm. Symptoms include seizures, lethargy, nausea and...
Diabetic Neuropathy (Symptoms, Causes, Diagnosis, Treatment)
Diabetic neuropathy a condition in which nerve damage has occurred as a complication of diabetes. The pain from the nerve...
The shoulder is the most often dislocated joint in the body due to its mobility. Dislocation occurs when the head of the humerus...
Ebola (Ebola Virus Disease or Ebola Hemorrhagic Fever)
Ebola hemorrhagic fever (HF) is an often-fatal disease that causes fever, headache, vomiting, diarrhea, sore throat, stomach...
Although a fever technically is any body temperature above the normal of 98.6 F (37 C), in practice, a person is usually not...
The most common food allergies are to eggs, nuts, milk, peanuts, fish, shellfish, strawberries and tomatoes. Symptoms and signs...
Graft Versus Host Disease (GVHD)
Graft versus host disease (GVHD) is a condition that happens when immune cells from transplanted donor tissue attack the...
Guillain-Barré Syndrome is an autoimmune disease of the nervous system due to damage to the myelin sheath around nerves....
Heat Rash (Symptoms, Pictures, Treatment, Remedies)
Heat rash is a skin irritation caused by excessive sweating. It can occur at any age and it appears as a rash that itches or...
HIV vs. AIDS
Human immunodeficiency virus causes HIV infection. Acquired immunodeficiency syndrome (AIDS) is a condition that results after...
Iron is a mineral our bodies need. Iron deficiency is a condition resulting from not enough iron in the body. It is the most...
Is MS Contagious? (Multiple Sclerosis)
Multiple sclerosis, or MS, is a degenerative disease of the covering around the nerves in the central nervous system (CNS)....
Kidney Infection (Pyelonephritis) Symptoms, Signs, Causes, Treatment
Kidney infection (pyelonephritis) usually is caused from bacteria that have spread from the bladder from a UTI (urinary tract...
Knee injuries, especially meniscus tears, are common in contact sports. Symptoms and signs of a torn meniscus include knee pain,...
Lassa fever is a viral hemorrhagic fever that causes flu-like symptoms. Ribavirin is the standard treatment for Lassa fever....
Lumbar Spinal Stenosis
Lumbar stenosis can be caused by degenerative arthritis (the most common cause), tumor, infection, or metabolic disorders...
Malaria is a disease that is spread by the bite of an infected Anopheles mosquito. Malaria symptoms include fever, chills,...
Marfan syndrome is hereditary (genetic) condition affecting connective tissue. A person with Marfan syndrome may exhibit the...
Encephalitis is a brain inflammation that causes sudden fever, vomiting, headache, light sensitivity, stiff neck and back,...
Migraine headaches are severe headaches that are sensitive to light, sounds, and smells. Some people who suffer from...
Multiple myeloma is a form of cancer that develops in plasma cells, the white blood cells that make antibodies. Symptoms include...
Multiple Sclerosis (MS Symptoms, Causes, and Life Expectancy)
Multiple sclerosis or MS is an autoimmune disorder in which brain and spinal cord nerve cells become demyelinated. This damage...
Muscle spasms are involuntary muscle contractions that come on suddenly and are usually quite painful. Dehydration, doing...
Myasthenia gravis, a chronic autoimmune neuromuscular disease. Varying degrees of weakness of the voluntary muscles of the body...
Non-Hodgkin's lymphoma is cancer of the lymphatic system, a vital part of the body's immune system. Symptoms and signs include...
Norovirus infection causes stomach flu, or gastroenteritis. It's a very contagious illness with symptoms that include nausea and...
Palpitations (Causes and Symptoms)
Palpitations are uncomfortable sensations of the heart beating hard, rapidly, or irregularly. Some types of palpitations are...
Peripheral Vascular Disease (PVD Symptoms, Signs, Causes, Treatments)
Peripheral vascular disease (PVD) refers to diseases of the blood vessels (arteries and veins) located outside the heart and...
Plague (Black Death)
Plague is an infectious disease caused by the bacteria Yersinia pestis. Transmission to humans occurs via fleas that have bitten...
Polymyalgia rheumatica (PMR) is a disorder of the muscles and joints that causes pain and stiffness in the arms, neck, shoulders,...
Postherpetic neuralgia (PHN) is a painful complication of shingles. Symptoms include: severe pain, itchy skin, and...
Powassan Virus Disease
Powassan (POW) virus disease is a rare tick-borne disease that causes symptoms such as confusion, memory problems, fever,...
Rocky Mountain Spotted Fever (RMSF)
Rocky Mountain spotted fever is a tick-borne disease that causes symptoms and signs such as fever, rash, headache, and muscle...
Rotator Cuff Disease
Rotator cuff disease is damage to any of the four tendons that stabilize the shoulder joint. Shoulder pain and tenderness are...
Salivary Gland Cancer
Salivary gland cancer is cancer that affects the parotid glands, sublingual glands, or the submandibular glands. Risk factors...
Medical shock is a life-threatening medical condition. There are several types of medical shock, including: septic shock,...
The five types of spondylolisthesis include dysplastic, isthmic, degenerative, traumatic, and pathologic. The most common symptom...
Stroke (Signs, Symptoms, Warning Signs)
A stroke is an interruption of the blood supply to part of the brain caused by either a blood clot (ischemic) or bleeding...
Tennis Elbow (Lateral Epicondylitis)
Tennis elbow is also known as lateral epicondylitis. Symptoms of tennis elbow include tenderness and dull pain of the outer...
A tension headache s one of the most common types of headaches, and the exact cause is not known. Factors that may contribute to...
Thoracic Outlet Syndrome (TOS)
Thoracic outlet syndrome is a condition where symptoms are produced from compression of nerves or blood vessels because the...
Ticks are known transmitters of disease to humans and animals. Tick-borne diseases include Lyme disease, Rocky Mountain spotted...
A torn meniscus (knee cartilage) may be caused by suddenly stopping, sharply twisting, or deep squatting or kneeling when lifting...
Viral Hemorrhagic Fever
Viral hemorrhagic fever(s), or VHFs are a group of illnesses caused by distinct families of viruses. Many of these viruses are...
Vitamin D Deficiency
Vitamin D deficiency has been linked with rickets, cancer, cardiovascular disease, severe asthma in children and cognitive...
West Nile Virus
West Nile virus (West Nile encephalitis) is a brain infection caused by a virus. People become infected with the virus after...
Yellow fever is an infectious disease transmitted by infected mosquitoes. Side effects are rare with the yellow fever vaccine....
Other Causes of Weakness
- Congenital Myopathies
- Electrolyte Imbalances
- Malignant Tumors
- Muscle Disease Medications
- Muscular Dystrophy
- Myotonic Dystrophy
- Nerve Impingement
- Poisoning (Organophosphates)
Examples of Medications for Weakness
- pyridostigmine (Mestinon)
Find out what women really need.