What is a High BUN/Creatinine Ratio? Causes, Symptoms, Risks (2024)

• Introduction
  • What is a BUN creatinine ratio?
• Causes
  • What causes BUN/creatinine ratio high levels?
• Factors
  • What factors can increase or decrease BUN creatinine ratio?
• FAQs
  • Frequently asked questions (FAQs) about BUN creatinine ratio

What is a BUN creatinine ratio?

Blood urea nitrogen (BUN) and creatinine tests are blood tests performed as part of routine health screening. These tests help assess how well your kidneys are functioning. If your doctor suspects any kidney conditions, you will be advised to go for BUN tests.

A high BUN to creatinine ratio may be due to conditions that lead to decreased blood flow to the kidneys. Read on to learn more about its causes, symptoms, and risks.

BUN

BUN measures the amount of urea in your blood. Urea nitrogen is the waste product formed as your liver breaks down the proteins in foods you eat; this protein breakdown creates BUN.

Usually, BUN is removed by your kidneys. If your kidneys are not functioning properly, the BUN gets stored, resulting in increased BUN levels.

Creatinine

While BUN levels may vary, creatinine blood levels are mostly stable. Creatinine is a waste product formed as a result of muscle wear and tear. Creatinine is produced from creatine, a protein that helps produce energy for muscle contractions.

Creatinine is removed from the body by the kidneys. When there is an abnormal function of the kidneys, creatinine levels increase in the blood.

BUN/creatinine ratio

BUN/creatinine ratio is the concentration of BUN and creatinine in blood, in comparison to each other. A BUN to creatinine ratio is used to check health issues such as dehydration, kidney diseases, intestinal bleeding, and other conditions.

What causes BUN/creatinine ratio high levels?

The normal ratio of BUN to creatinine is between 10:1 and 20:1. Typically, normal BUN and creatinine levels will result in a normal BUN/creatinine ratio, and changes in only one or the other value will result in an abnormal BUN creatinine ratio. However, elevated BUN and creatinine values will result in a normal ratio if they increase in the same proportion, so all three values are important for diagnosis.

A high BUN/creatinine ratio in your blood tests may result from three reasons: elevated BUN and normal creatinine, normal BUN and low creatinine, or both BUN and creatinine elevated, but BUN is disproportionately higher. On the other hand, BUN creatinine ratio blood test low results may be because your BUN is low with creatinine normal, BUN normal with high creatinine, or both values low with BUN proportionately lower than creatinine.

A high BUN to creatinine ratio may result from conditions that decrease blood flow to the kidneys, such as congestive heart failure or dehydration.

BUN to creatinine ratios can also increase with both age and reduced muscle mass.

What causes abnormal BUN creatinine levels?

Abnormal BUN to creatinine levels are due to the underlying diseases and are typically accompanied by symptoms of the conditions.

Causes of BUN/creatinine ratio high levels include:

• Dehydration: Increases both BUN and creatinine but increases BUN more.
• Intestinal bleeding: Blood loss reduces blood volume and circulation to the kidney, increasing BUN, Additionally, the blood in the intestine, which has high protein, is digested.
• Hyperthyroidism: Increases BUN and lowers creatinine levels.
• Congestive heart failure: Increases reabsorption of urea in the kidneys and consequently, increases BUN.
• Kidney diseases: These can increase both BUN and creatinine.
• Medications: Antibiotics such as tetracycline and corticosteroids used to treat inflammation can increase BUN/creatinine ratio.

Causes of low BUN to creatinine levels include:

• Malnutrition, with low protein intake: Low protein intake reduces BUN production.
• Hypothyroidism: Increases creatinine levels.
• Advanced liver diseases: The liver cannot break down protein to produce urea, so BUN goes down.
• Sickle cell anemia: Kidneys reabsorb too little urea, and urea is eliminated in urine, lowering BUN.
• Rhabdomyolysis: A disease in which muscles break down rapidly, increasing creatinine levels.
• Kidney damage: Kidneys are unable to filter out creatinine effectively and blood creatinine levels go up.
• Medications: Some drugs including acetazolamide and diuretics for conditions such as glaucoma, altitude sickness, and heart failure can alter BUN levels.

What factors can increase or decrease BUN creatinine ratio?

Many conditions can increase or decrease BUN creatinine ratio. If you are diagnosed with an abnormal BUN/creatinine ratio, treating the underlying condition should usually bring the balance back to normal. In addition to treating your condition, your physician may suggest ways to alter your BUN and/or creatinine levels.

The following are factors that impact BUN and creatine levels:

• Factors that increase BUN
  • Increase dietary protein with beans or lean meats, if you have low BUN
  • Avoid or limit alcohol consumption, it can increase BUN
• Factors that reduce BUN
  • Proper hydration can decrease BUN
  • Obesity and high BMI, which can cause kidney dysfunction, causes low BUN
• Factors that reduce creatinine
  • Not consuming creatine and creatine-based food
  • Increased dietary fiber
  • Weight loss, which can improve kidney health
• Factors that increase creatinine
  • Increased exercise and physical activity
  • Increasing dietary intake of creatine

Frequently asked questions (FAQs) about BUN creatinine ratio

What does it mean if my BUN creatinine ratio is high?

If your BUN creatinine ratio is high, it means, your urea levels are much higher than they should be in comparison with creatinine. Blood nitrogen urea is a waste product from digestion of protein by the liver, and creatinine is a waste product from creatine, a protein that muscles use for energy. BUN and creatinine are both primarily excreted in the urine. Both BUN and creatinine values individually, and as a ratio in relation to each other, are used for diagnosis of various conditions.

A high BUN creatinine ratio may result from high BUN and normal creatinine, a normal BUN and low creatinine, or both BUN and creatinine elevated, with BUN disproportionately higher. The individual values of BUN and creatinine, as well as the ratio are important for a correct diagnosis. Additional diagnostic tests may also be required for diagnosis of the underlying cause for a high BUN/creatinine ratio, and appropriate treatment.

A high BUN creatinine ratio with both BUN and creatinine elevated may mean your kidneys may not be functioning as well as they should. This may be from kidney injury due to dehydration, impaired blood flow to the kidneys, urinary obstruction, kidney disease, liver disease or congestive heart failure. Normal BUN with low creatinine may mean inadequate creatine intake, or may be from age, loss of weight and/or muscle mass.

BUN elevation with normal creatinine may mean you have gastrointestinal (GI) bleeding, because blood is high in protein, and is digested in the intestines. BUN creatinine ratio test can also help in identifying the location of the intestinal bleed, because proteins are digested in a particular region of the intestines, and bleeding below this region will not increase the BUN levels. In patients with acute pancreatitis, a high BUN/creatinine ratio may mean an increased risk for worsening of condition.

What is a dangerously high BUN/creatinine ratio?

According to the BUN/creatinine ratio chart, normal BUN/creatinine ratio typically falls between 10:1 or 20:1, and with age it is likely to be on the higher end of normal. Values consistently around 20:1 may be early warning signs of kidney disease. Any value above 20:1 indicates that you are dehydrated, and may also be developing kidney-related or other health issues. A BUN/creatinine ratio of 50:1 or above is dangerously high that requires immediate medical attention. Ratios of 100:1 and above indicate serious kidney dysfunction.

Should I be worried if my BUN level is high?

You should definitely seek proper diagnosis and necessary treatment if your BUN level is high. High BUN level may mean simple dehydration that can be easily corrected with adequate hydration, but also more serious conditions such as kidney disease, congestive failure, or an intestinal bleed. Your diagnosis and treatment will be based on your symptoms, and other diagnostic tests in conjunction with your BUN level readings.

Can dehydration cause a high BUN creatinine ratio?

Dehydration can cause a high BUN creatinine ratio, because, dehydration reduces the water available for kidney to excrete waste products. Dehydration can elevate both BUN and creatinine, but some quantity of BUN is reabsorbed in the kidneys, while creatinine is not reabsorbed. Thus, BUN in the blood increases to a higher extent than creatinine, resulting in a high BUN creatinine ratio.

How do you fix a high BUN creatinine ratio?

Treatment for a high BUN creatinine ratio will depend on the individual levels of BUN and creatinine and the underlying cause for the imbalance in the BUN and/or creatinine levels. Diagnosis may include other tests in conjunction with BUN/creatinine ratio blood test. Treatment may require medications, and your physician may also suggest dietary and other ways to bring back the normal balance in your BUN/creatinine ratio.

How to calculate BUN creatinine ratio

BUN/creatinine ratio is usually calculated by the testing laboratory and given as part of the bloodwork results. To calculate BUN creatinine ratio, the individual levels of BUN and creatinine are measured in milligram/deciliter (mg/dL) of blood. Dividing the BUN value by the creatinine value gives you the BUN creatinine ratio.

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WebMD. “What is a Blood Urea Nitrogen Test?” Reviewed October 30, 2023. https://www.webmd.com/a-to-z-guides/blood-urea-nitrogen-test

Acutecaretesting.org. “Urea and creatinine concentration, the urea:creatinine ratio.” Dated October 2016. https://acutecaretesting.org/en/articles/urea-and-creatinine-concentration-the-urea-creatinine-ratio

Simple Nursing. “BUN levels: What to Look for in a Blood Test.” Dated: Jan 24, 2023. https://simplenursing.com/bun-levels/