Protein Deficiency: Signs, Causes, and Treatment

Most people in the U.S. get more than enough protein. But how much protein you need depends on where you are in life, your activity level, and other medical conditions. Some experts believe that older adults and children may not be getting enough.

So, how do you know if you’re getting enough protein? There are ways to calculate how much you need. But most people probably don’t give much thought to their protein intake on a daily basis. 

Having a protein deficiency can be serious. So, knowing the signs of a protein deficiency can alert you to a potential problem and help you take action. 

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What are the most common signs of protein deficiency?

You probably won’t experience any signs or symptoms from not getting enough protein in the short term. But if you don't meet your protein needs for a long time, you may begin to have signs of a protein deficiency. These signs may include:

• Brittle nails and/or hair

• Bone fractures

• Loss of muscle mass

• Weakness in the muscles or body in general

• Extreme hunger

You may also experience changes like:

• Becoming sick more often due to a weakened immune system

• Mood changes

• Difficulty thinking straight

And, over time, protein deficiency can cause:

• Development of fatty liver disease

• Delayed growth in children

What should you do if you have signs of protein deficiency?

It’s best to see a primary care provider if you’re concerned about protein deficiency. They can talk with you about any other signs or symptoms and your medical history. This can help determine the next steps for testing and/or treatment (more on this below).

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What causes a protein deficiency?

There are many possible causes of protein deficiency. These can include:

• Not getting enough protein in your diet: This may be due to an eating disorder, lack of food access, or dietary restrictions. Each of these things may severely limit your protein intake. 

• Certain gastrointestinal disorders: Some conditions prevent your body from absorbing protein properly. Examples include Crohn’s disease and celiac disease.

• Bariatric surgery: Bariatric surgery reduces how much food can be eaten at one time and changes your food preferences. Research suggests that protein is the most common macronutrient that patients don’t get enough of after surgery. 

• Diabetes: Having uncontrolled Type 1 diabetes may increase your risk of protein deficiency. This is because the lack of insulin causes your body to start breaking down protein stores. 

• Liver diseases: Your liver makes many important proteins. So, when it’s not working properly, your body creates less protein. In addition, having liver disease like cirrhosis can lead to malnutrition due to poor appetite and impaired nutrient absorption. 

• Kidney disease: Kidney damage can cause protein to leak out of your blood and go into your urine. People with chronic kidney disease often have different protein needs, depending on the severity of their condition. 

• Long-term injury or infections: Serious injuries and infections increase your body’s protein needs. They cause your body to be in a catabolic state. This is when your body breaks down mass and loses protein.

• Severe burns: Burns cause your body to lose protein, as does the healing process. 

How much protein do you need?

The Recommended Dietary Allowance (RDA) for protein for healthy adults is 0.8 g of protein per kilogram of body weight each day. When translated to pounds, this equals about 0.36 g of protein per pound of body weight. So, for someone who weighs 180 lbs, this would equal about 65 g of protein. 

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But estimating your protein needs isn’t always that simple. How much protein you need can vary greatly based on different factors:

• Age: Older adults may need up to twice as much protein than younger adults, about 1.2 g to 2 g of protein per kilogram of body weight. This is because older adults have a natural decline in muscle mass. Children should also aim for more protein than healthy adults, at 0.95 g per kg of body weight. 

• Activity level: If you’re more active, your protein target is higher, at 1 g to 1.6 g per kilogram of body weight. This is especially true for people trying to build muscle. 

• Current health conditions: For example, critically ill patients may need up to 1.5 g to 2 g of protein per kilogram of body weight. As mentioned above, people with kidney or liver disease may also have different protein needs.

How is protein deficiency diagnosed?

There’s no single test to diagnose a protein deficiency. A healthcare professional will look at a combination of lab results and a review of your current diet. 

Lab tests

There are two main blood tests that can help indicate protein levels in the blood. These tests are:

1. Albumin: Albumin is the most prevalent protein in your blood. It makes up about half of your blood’s total protein content. 

2. Total protein test: This test measures the total amount of protein in your blood, including albumin and globulins. 

Your results of these tests show whether your levels are high or low, based on the normal range. But these tests shouldn’t be used alone to diagnose a protein deficiency. If you have an abnormal total protein test, you may need additional testing and/or health screening to get a proper diagnosis.

Diet review

Another way to help determine if someone is protein deficient is to estimate their average protein intake. This can be done by a healthcare professional, such as a dietitian. They’ll ask questions about what you eat on a daily basis. They can then add up the estimated grams of protein you may be consuming and compare it to your estimated daily needs. 

Keep in mind that protein deficiency due to poor intake is extremely rare in the U.S. This is because many foods — both plants and animals alike — can contribute to your total protein intake. People who’re eating a wide variety of foods are generally able to meet their protein needs. 

How is protein deficiency treated?

Treatment for protein deficiency depends on the cause. For someone who hasn’t been eating enough protein, it’s best to increase the amount of protein in your diet. Examples of high-protein foods include: 

• Meats

• Fish

• Eggs

• Nuts

• Beans

You may need to introduce protein slowly to give your body time to adapt. 

If you have a protein deficiency due to a medical condition, eating more protein probably won’t be helpful. It’s best to discuss your protein needs with a dietician or someone on your medical team with expertise in your condition. For example, many gastrointestinal disease clinics have an expert available for things like this. They’ll work with you to come up with a plan to improve and monitor your protein status.

How serious is protein deficiency?

But because protein deficiency is rare, it’s generally not something most healthy adults need to worry about. That said, for some people, having a protein deficiency can be serious. 

The outcome of a protein deficiency depends on how long it has been going on and what else is happening in your body. If your protein deficiency is short term, you may be able to recover without lasting problems. 

It becomes more serious, though, if your protein deficiency is longer term or is due to overall malnutrition. For example, children can experience growth problems. And older adults can lose strength and independence.

Having a protein deficiency can also delay your body’s natural healing process. It can lead to disease-related malnutrition. This causes delayed healing and possible complications. That’s why getting enough protein, calories, and nutrients in your diet is essential. 

Kwashiorkor and marasmus are the most severe diseases of protein malnutrition. They’re more common outside of the U.S. and in young children experiencing poverty or famine. These types of protein malnutrition put them at risk for infections, stunted growth, and physical and mental disabilities. These conditions can be life-threatening if not treated. 

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Written by:

Joanna Foley, RD

Joanna Foley, RD, is a registered dietitian (RD) and the owner of joannafoleynutrition.com, a private nutrition consulting business. She has previously worked as a clinical dietitian and outpatient renal dietitian.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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