Parkview Health Logo

Weakness and fatigue: Understanding the difference

Last Modified: June 20, 2023

Family Medicine


Often, when we hear people speak about their symptoms when they are ill or feeling under the weather, the first things they mention are feeling weakness and fatigue. Though the two often come together, they are very different and can both tell a unique story about an illness. Being able to communicate specifics around these sensations can help you and your doctor narrow down the possible causes and course of treatment.

In this blog, we will discuss the difference between weakness and fatigue, how to care for these symptoms and when it’s appropriate to inform your provider.


Generally speaking, weakness is a lack of physical or muscle strength. When experiencing body weakness, you feel like you need to use extra effort to move your arms, legs or other muscles. Typically, your brain will still function normally, but your physical body and muscles feel the loss of strength.

Weakness often occurs after you've done too much activity at one time. For instance, maybe you took an extra-long hike. You may feel weak and tired, or your muscles may be sore. These symptoms usually go away within a few days.

In rare cases, muscle weakness may be caused by another health problem, such as:

  • A problem with the minerals (electrolytes)–like potassium or sodium–found naturally in the body.
  • Infections, such as a urinary tract infection or a respiratory infection.
  • Problems with the thyroid gland, which regulates the way the body uses energy.
  • Rare nerve disorders, such as Guillain-Barré syndrome.

It’s important to notice and make note of muscle weakness that is slowly getting worse or if you lose muscle function in one area of the body. These can be signs of a stroke or a problem with the spinal cord or a nerve.


Fatigue is a feeling of tiredness, exhaustion or lack of energy. You may feel mildly fatigued because of overwork, poor sleep, worry, stress, boredom, lack of exercise or poor diet. Many medical problems, such as viral infections, can also cause fatigue.

Emotional problems, especially anxiety and depression, are often the cause of fatigue. Any illness may cause fatigue and the fatigue usually goes away as the illness clears up. Most of the time, mild fatigue occurs with a health problem that will improve with home treatment, and does not usually require a visit to a doctor.

Fatigue that lasts longer than 2 weeks usually requires a visit to a doctor. This type may be caused by a more serious health problem, like:

Caring for weakness and fatigue

If you are experiencing weakness and fatigue along with other symptoms, look closely at those symptoms. Typically, you can improve your discomfort and get to feeling better with at-home treatments. Here are some things you can try:

  • If you can, stay home when you’re sick. Try to stay away from others and get some extra sleep.

  • Go slowly. Return to your usual activities slowly to avoid making the fatigue last longer.

  • Stay hydrated. Be sure to drink extra fluids to avoid dehydration.

  • Listen to your body. Switch between rest and exercise. Gradually increasing your activity may help decrease your fatigue.

  • Limit medicines that might add to fatigue. Medications like cold and allergy medicines often cause fatigue.

  • Improve your diet. Eat a balanced diet to increase your energy level. Don't skip meals.

  • Beware of substances that may cause fatigue. Reduce your consumption of alcohol or other drugs, such as caffeine or nicotine.

  • Cut back on screen time. Spend those precious minutes with friends or try new activities to break the fatigue cycle.

  • Get a good night's sleep. This may be the first step toward controlling fatigue. Establish good sleep hygiene by limiting sound and light disturbances, avoiding eating just before you go to bed, staying off of technology at least 30 minutes before you get into bed and only using your bed for sleep.

Weakness: When to call

Call your doctor immediately or seek immediate medical care if:

  • You have new or worsening weakness.
  • You are dizzy, lightheaded or you feel like you might faint.
  • You lose muscle function in one area of the body. This can be a sign of a stroke or of a problem with the spinal cord or a nerve.

Fatigue: When to call

Watch closely for changes in your health, and be sure to contact your doctor if:

  • You have new symptoms, such as fever or a rash.
  • Your fatigue gets worse.
  • You have been feeling down, depressed or hopeless, or if you lose interest in things that you usually enjoy.
  • You are not getting better, as expected.

When in doubt, don’t hesitate to reach out to your primary care provider if you notice any concerning changes to your energy level or mood.









Copyrighted material adapted with permission from Healthwise, Incorporated. This information does not replace the advice of a doctor.

Related Blog Posts

View all posts