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14 Conditions That Can Cause Muscle Weakness

 Muscle weakness is a weird symptom, not because it’s unusual on its own, but because we somehow blame ourselves for experiencing it, although it has little to do with how much or how often we exercise. In many cases, muscle weakness goes hand in hand with fatigue and exertion of the body’s natural reserves, but sometimes, weak muscles can be a sign that something’s wrong with your hormones, your nervous system and many other, seemingly not connected organs. This way, pain or weakness in the muscles can be an important signal that something’s wrong with the body, be it a complication of diabetes, kidney problems, MS, or nerve damage. All 14 of the following can cause muscle weakness:

1. Electrolyte Imbalances

Causes of Muscle Weakness Electrolyte Imbalance
A small thing like not drinking enough or drinking too much water can wreak havoc on your body. An imbalance of such electrolytes as calcium, magnesium, sodium, and potassium in the blood can make you feel terrible and produce the following symptoms:
  • Bone disorders
  • Pain and muscle weakness
  • Anxiety
  • Increased thirst
  • Insomnia
  • Constipation and diarrhea
  • Abdominal pain
  • Dizziness and fatigue
  • Joint pain and numbness.

These imbalances can typically be adjusted by dietary changes, such as moderate sodium intake and adequate daily water intake. Some medications (e.g. blood pressure medications and antibiotics) may increase your risk of an electrolyte imbalance, so consult your physician if you need to supplement these electrolytes to compensate for the effects of your medications.

2. Hypothyroidism

Causes of Muscle Weakness Hypothyroidism
An underactive thyroid, too, can be the underlying cause of weak and tender muscles. These patients often report that being active or exercising can further worsen the symptoms. Patients typically also experience weight gain, have a slow heart rate and often suffer from depression. Hormone therapy is necessary to improve the symptoms.

3. Sleep Disorders

Causes of Muscle Weakness Sleep Disorders
Oftentimes, we experience muscle weakness because of fatigue, and nearly all sleep disorders (e.g. narcolepsy, insomnia, etc.) make you feel extremely tired and lacking energy. Sleep problems may also mean that you’re spending more time in bed, which, in turn, can make your muscles somewhat weaker as well. This is also the reason why people who stay in bed due to any health condition often experience muscle weakness.

4. Rheumatoid Arthritis

Causes of Muscle Weakness Rheumatoid arthritis
This chronic inflammatory condition targets the joints, typically in the hands and feet, making them stiff, swollen and painful. The symptoms aren’t limited to the joints, however, and patients also often suffer from muscle pain and weakness, fatigue and even depression. We discuss these symptoms and more facts about arthritis here.

5. Diabetes

Causes of Muscle Weakness Diabetes
Diabetes is a particularly dangerous condition, as the abnormal levels of insulin and sugar in the blood can affect tissues in the entire body. A particularly dangerous effect is nerve degeneration, which can make you lose sensation, experience pain and weakness in various body parts, typically in the limbs. Impaired mobility and fatigue often accompany and further exacerbate the pain and weakness.

6. Fibromyalgia

Causes of Muscle Weakness Fibromyalgia
Fibromyalgia is a chronic condition that is more common in women than in men. Patients suffering from fibromyalgia typically experience pain in joints and muscles throughout the body. Some additional symptoms of fibromyalgia can be seen in the image above. The causes of this condition are unknown, but medical researchers suggest that there is both a biological and psychological component to it.

7. Several Infections

Causes of Muscle Weakness Infections
Do you know that feeling of fatigue and muscle pain that plagues your entire body when you’re down with a cold? This is exactly the kind of feeling people can experience during any infection, it’s only the severity that varies. All the most dangerous and terrible infections in history, such as HIV, syphilis, tuberculosis, toxoplasmosis, and Lyme disease can affect our muscle strength, as it takes insane amounts of energy to fight off these infections.
In some cases, patients continue feeling residual muscle weakness even after post-recovery. Polio patients, for example, can experience something called the post-polio syndrome, which is the gradual weakening of the affected muscles after recovery.

8. Kidney Disease

Causes of Muscle Weakness Kidney Disease
At first glance, the connection between muscle strength and kidney health may escape you, but it turns out that kidney infections, kidney stones, and other kidney diseases may have a significant effect on our muscle strength. This is because malfunctioning kidneys are worse at filtering out metabolic waste products than healthy kidneys, and these can build up in the soft tissues, such as your muscles and fatty tissues. These composites, in turn, can affect the functioning of the muscles, causing weakness, twitching, and pain.

9. Lupus

Causes of Muscle Weakness Lupus
Systemic lupus erythematosus (SLE), or simply lupus is a dangerous autoimmune condition, which means that the immune system mistakes your body for a foreign object and starts attacking different tissues in the body. Damage caused by immune cells to the nerves and muscles can cause pain and weakness in the muscles.
Other symptoms of SLE include:
  • A butterfly-shaped rash on the cheeks
  • Photosensitivity
  • Mouth ulcers
  • Fatigue
  • Painful and swollen joints
  • Fever
  • Chest pain, etc.

10. Neurological Conditions

Causes of Muscle Weakness Neurological Conditions
As you will know, one of the functions of the nerve endings in our body is transmitting information about our body to our central nervous system (CNS, includes the brain and spinal cord), be it pain, movement, temperature or any other type of signal.
When these nerves are damaged at any point in this route, this can lead to a loss of sensation in the body, including the muscles. Common neurological conditions that affect muscle functioning are multiple sclerosis, spondylosis, and even botulism (nerve damage as a result of exposure to the chemical toxin botulinum). Spinal cord injuries, too, can result in muscle weakness, depending on the location of the injury.

11. Chronic Fatigue Syndrome

Causes of Muscle Weakness Chronic fatigue syndrome
It’s likely your first time hearing about this mysterious syndrome, which is mysterious not because most people don’t know it exists, but rather because even doctors themselves don’t know what’s causing it.
Patients suffering from chronic fatigue syndrome (CFS) constantly feel tired and often have sleep problems. Along with these main symptoms, they sometimes also experience the following symptoms:
  • Muscle weakness
  • Pain
  • Dizziness
  • Problems concentrating.

12. Certain Medications

Causes of Muscle Weakness Medications
That’s right, in this lone case, you can absolutely blame your medication for making your muscles weaker. This doesn’t mean you should discontinue them, however. Instead, we suggest consulting your physician and inquiring whether they can replace it with another medication or adjust the dosage of the current medication.
Common medicines that cause muscle weakness include:
  • Penicillin
  • Statins
  • Sulfonamide antibiotics
  • NSAIDs (ibuprofen or naproxen)
  • Antithyroid medications
  • Chemotherapy medications
  • Corticosteroids.

13. Addison’s Disease

Causes of Muscle Weakness Addison’s Disease
Cortisol and aldosterone insufficiency in the adrenal gland is known as Addison’s disease, and patients suffering from this condition often feel fatigue and muscle weakness, but other symptoms, such as stomach pain and weight loss are also often present. But definitely the strangest symptom of this condition is sudden skin tanness, which we discuss in more detail in this article about strange skin symptoms that point to a different condition.

14. Anemia

Causes of Muscle Weakness Anemia

Anemia is a condition that occurs when hemoglobin levels in the blood are too low and the blood cannot supply optimal quantities of oxygen to the cells. There are many types of anemia, some are genetic, whereas others are caused by an iron deficiency. Because anemia patient's blood is less efficient at supplying the muscles with oxygen, it may result in muscle weakness, but also other symptoms, such as:

  • Dizziness
  • Shortness of breath
  • Irregular heartbeat
  • Headaches.

​Depending on the type of anemia, the treatment of the condition will vary, but sufficient iron intake or supplementation often does the trick. Here is a handy list of foods rich in iron.

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