Do You Lose Muscle When You’re Sick? What the Science Says

Have you ever noticed how hard it feels to build muscle and feel strong — and how easy it feels to lose muscle when you skip a few days at the gym? This feeling that you have to either “use it or lose it” seems especially true when you’re sick and are forced to take a break from the gym. 

But are you actually losing muscle when you’re sick? Or, does it just take longer for your strength to recover once your symptoms are gone? 

Muscle loss (also known as muscle atrophy) is quite common when you’re sick — and it can happen a lot faster than you’d expect. Here’s what you can expect from your muscles when you’re sick, and how to regain muscle mass after illness.

Will you lose muscle from being sick?

Yes, you’ll likely lose muscle when you’re sick, including both a loss in the size and strength of your muscles. But this is typically seen with serious or long illnesses. Most people won’t lose a significant amount of muscle from a mild illness. 

Muscle loss is common if you have a critical illness. Critical illnesses are severe illnesses that usually require treatment in a hospital. 

Studies show that critical illness is associated with muscle loss. This happens because the body is trying to preserve critical functions. It stops building and maintaining muscle in order to keep up with more important demands.

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In one study, people experienced 15% loss of muscle within the first week of a critical illness. And in another study, people requiring treatment in an intensive care unit (ICU), lost 20% of their muscle mass within 10 days. 

When it comes to noncritical illnesses that don’t require hospitalization — like the cold, a mild COVID-19 infection, or the flu — most people won’t experience any significant muscle loss. 

It’s also important to keep in mind that many people lose muscle as they recover from a long or serious illness. During recovery, people usually spend more time in bed and can’t move around as easily. This leads to muscle atrophy, a condition where your body breaks down more protein than it builds. 

That’s why experts recommend activity even as people recover from illness. This can mean getting out of bed and into a chair or taking a few steps in your room. Every little bit of movement helps muscles keep their strength. 

Why does muscle loss happen during illness?

As mentioned above, when you’re sick, muscle loss can happen because you’re unable to move around or stay active. 

But there are other reasons you can lose muscle during an illness. Lack of nutrition, inflammation, and medications can also damage muscle tissue and lead to muscle loss. 

Not getting enough nutrition

When you’re sick, you may not feel like eating. And symptoms like nausea can make it difficult to keep food and liquids down. If your body can’t use energy from food, it may need to break down muscle instead to fuel your immune system. People with critical illnesses need specialized nutrition during a critical illness.

Widespread inflammation

Inflammation can contribute to muscle breakdown. Researchers think that the inflammatory response blocks pathways that help build muscle, and supports pathways that help break it down. 

Medication side effects

Some medications can cause muscle loss. Statins and corticosteroids are examples of two medications that can cause muscle loss and weakness. People may need higher doses of their medications when they are sick. They may also need to start new medications that may cause muscle breakdown. This can lead to further muscle loss during an illness. 

How long does it take to lose muscle?

The timeline for muscle loss can differ from person to person. However, research shows that muscle loss starts to happen within 10 to 14 days of being immobile or on bedrest.

But several factors can influence how long it takes to lose muscle. These factors include the following.

Muscle loss happens faster if you are critically ill

A review of studies found that healthy individuals who were on bedrest lost about 0.5% of their muscle daily during the 2 weeks of their illness. On the other hand, critically ill individuals lost around 2% of their muscle each day during the same time frame.

Older adults lose muscle faster when they are sick 

You naturally lose muscle mass as you get older. This is called sarcopenia. Since older adults have fewer muscle reserves, they tend to lose muscle mass more quickly than younger adults, especially if they are sick or on bedrest.

How to maintain muscle mass while you’re sick

It’s important to rest when you’re sick. And if you’re critically ill or recovering from a critical illness, you may not have a lot of control over how much you’re allowed to move.  

But there are some things you can try to minimize muscle loss as much as possible when you’re sick or recovering.

Work with physical therapists 

Work with physical therapists and other healthcare professionals to maximize your mobility. They can help you find ways to safely stay active, whether that’s taking steps or getting out of bed and into a chair. Your team may also recommend mobility devices, like walkers, to help you move around safely. 

Focus on your nutrition 

While foods won’t cure your illness, what you eat and drink can support your immune system and ease symptoms so you can be more comfortable. You may need to work with a nutritionist as you recover from a critical illness to make sure you’re getting everything you need in your diet. Many people need more protein as they recover. You may also need more vitamins and minerals, like iron, to help you recover from an illness.

Returning to the gym after sickness and safety tips

The path for returning to the gym after sickness looks different for everyone. It can depend on a lot of things, like how long you were sick and your goals for returning to activity. 

While there isn’t a one-size-fits-all approach to returning to exercise, here are some tips that can help:

• Take it slow. Start slowly with low-intensity exercises to see how your body responds to activity. Once you’re feeling OK, and don’t experience any increased fatigue or return of your symptoms, you can gradually increase your exercise intensity. 

• Focus on flexibility. You’ll probably feel stiff and sore after lying around for a few days to recover. Gentle mobility exercises support flexibility and range of motion in your joints. They’re a nice complement to other strength or cardio activities you’re easing back into.

• Listen to your body. Pay attention to how your body feels as you get back to your regular routine. If you notice that your symptoms return, new pain pops up, or feelings of lightheadedness or fatigue, it could mean you’re pushing yourself too hard.

• Reach out for professional help. Working with a healthcare professional like a physical therapist or your primary care provider can be really helpful. They can give you personalized and medically appropriate guidance on exercises and the best ways for you to return to activity.

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Written by:

Ashley Rawlins, PT, DPT

With over a decade of experience as a physical therapist, Ashley has established herself as a specialist in pelvic health. Her diverse career spans clinical practice, academia, and health content creation.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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