What is the cause of protein loss?

December 4, 2025 •

3 min read

Over 70% of hospitalized individuals over the age of 70 have hypoalbuminemia, a condition with low blood protein levels. Understanding what is the cause of protein loss is crucial for identifying underlying health issues and seeking appropriate treatment.

Quick Summary

Protein loss can result from multiple issues, including kidney damage that leaks protein into urine, liver disease that impairs protein synthesis, or malabsorption and malnutrition. Increased protein demand from severe burns, inflammation, or metabolic stress can also lead to deficiency.

Key Points

Kidney Disease is a Major Cause: Damaged kidney filters (glomeruli) can allow essential proteins to leak into the urine, a condition known as proteinuria.
Liver Dysfunction Impairs Production: Conditions like cirrhosis and hepatitis can significantly reduce the liver's ability to synthesize critical blood proteins, including albumin.
Malnutrition and Malabsorption Play a Role: Insufficient protein intake from diet (malnutrition) or digestive disorders that prevent proper absorption (malabsorption syndromes) can lead to protein deficiency.
Inflammation Increases Demand: Severe infections, burns, or chronic inflammatory diseases raise the body's metabolic needs, causing increased protein breakdown and subsequent loss.
Treatment Depends on the Cause: A diagnosis by a healthcare professional is crucial, as treatment for protein loss must target the underlying condition rather than simply increasing dietary protein.
Look for Symptoms: Signs like fatigue, swelling (edema), hair loss, and weakened immunity can all signal an issue with protein levels.

Introduction to Protein and Protein Loss

Proteins are fundamental building blocks for virtually every part of the human body, from muscles and bones to enzymes and hormones. A consistent daily supply is necessary to maintain vital functions, as the body doesn't store protein long-term. A deficiency, known as hypoproteinemia, can occur from insufficient intake or if the body loses or fails to produce protein properly. While dietary protein deficiency is uncommon in developed countries, underlying medical conditions frequently cause protein loss.

Medical Causes of Protein Loss

Protein loss is often a symptom of a more serious medical condition affecting metabolism, absorption, or excretion. Common causes include:

Kidney Diseases (Proteinuria)

Kidney dysfunction is a frequent cause of protein loss. Healthy kidneys filter waste while retaining proteins. Damaged filtering units (glomeruli) can leak protein, especially albumin, into the urine, resulting in proteinuria.

Glomerulonephritis: Inflammation of the glomeruli impairs filtering.
Nephrotic Syndrome: This set of symptoms indicates glomerular damage.
Diabetes and High Blood Pressure: These are leading causes of chronic kidney disease (CKD) and progressive proteinuria.
Other Conditions: Lupus, preeclampsia, and genetic disorders like polycystic kidney disease can also cause proteinuria.

Liver Disease

The liver synthesizes proteins like albumin. Disease can lead to insufficient production.

Cirrhosis: Liver scarring reduces protein synthesis capacity.
Hepatitis: Chronic viral hepatitis can impair liver function.
Protein-losing Enteropathy: In some liver diseases, gut changes cause excessive protein loss.

Malnutrition and Malabsorption Disorders

Protein issues can arise from insufficient intake or impaired absorption.

Malnutrition: Low protein intake from poverty, restrictive diets, or eating disorders can lead to deficiency. Kwashiorkor is a severe form.
Malabsorption Syndromes: Small intestine conditions hinder nutrient absorption.
- Celiac Disease: Gluten damages the small intestine, compromising protein absorption.
- Inflammatory Bowel Disease (IBD): Chronic inflammation interferes with protein absorption.

Increased Protein Demand

Severe conditions can dramatically increase the body's need for protein.

Severe Burns: Healing requires massive protein for tissue repair.
Infections and Inflammation: Sepsis or surgery increase protein breakdown.
Advanced Cancer: Cachexia can lead to significant protein loss.

Comparing Causes of Protein Loss


Feature	Kidney Disease (Proteinuria)	Liver Disease (Impaired Synthesis)	Malnutrition (Inadequate Intake)
Primary Mechanism	Excess protein leaks from blood into urine due to damaged kidney filters.	Liver fails to produce enough protein due to damage and scarring.	Body does not receive enough protein from dietary sources to meet its needs.
Symptom Clues	Foamy urine, swelling (edema) in hands, feet, face.	Jaundice, ascites (fluid in abdomen), fatigue.	Weakness, fatigue, hair loss, muscle wasting.
Diagnosis	Urine tests (UACR), blood tests for kidney function (eGFR).	Blood tests measuring liver enzymes, albumin levels, and clotting factors.	Dietary history, physical examination, and blood tests for serum albumin.
Treatment Focus	Managing the underlying kidney disease, often with ACE inhibitors or ARBs.	Treating the liver condition and providing nutritional support.	Increasing protein intake through diet and supplements, addressing underlying issues like eating disorders.

Conclusion: Seeking a Diagnosis

Protein loss signals an underlying health issue, whether from kidney malfunction, liver problems, poor diet, or other severe conditions. Prompt diagnosis by a healthcare provider is crucial for effective treatment. While increasing dietary protein helps with malnutrition, it may not treat protein loss from organ-related diseases. A tailored approach based on the specific cause is necessary.

Learn more about hypoproteinemia and its causes from the Cleveland Clinic.

Frequently Asked Questions

Symptoms of protein loss can include swelling in the hands, feet, and face (edema), fatigue, dry skin, brittle hair, hair loss, and a weakened immune system leading to frequent infections.

Diagnosis involves a physical examination, dietary history, and various lab tests. Key tests include a blood test to measure total protein and albumin levels, and a urine test to check for excessive protein (proteinuria).

Yes, kidney disease is a major cause of protein loss. Damaged kidneys fail to properly filter blood and allow proteins, such as albumin, to leak into the urine, a condition called proteinuria.

Yes, the liver is responsible for synthesizing many of the body's proteins. Liver diseases like cirrhosis can severely impair this function, leading to low protein levels in the blood.

Inadequate dietary protein is a cause of protein deficiency, but it is rare in developed countries. It can occur with highly restrictive diets, eating disorders, or in cases of severe malnutrition.

Treatment depends on the underlying cause. Options can range from increasing dietary protein or taking supplements for nutritional deficiencies to managing kidney or liver disease with medication or other therapies.

Proteinuria is the presence of excess protein in the urine, which is a key sign of kidney damage. Hypoproteinemia is the medical term for low protein levels in the blood, which can be caused by proteinuria, reduced synthesis, or other factors.