From the Guidelines
An elevated Blood Urea Nitrogen (BUN) to Creatinine (Creat) ratio suggests possible pre-renal causes of kidney dysfunction, and it is essential to investigate and address the underlying cause to prevent further kidney damage and improve patient outcomes. This elevated ratio often indicates dehydration, decreased kidney perfusion, or increased protein breakdown in the body 1. The normal range for the BUN/Creatinine ratio is typically 10-20, and a ratio of 24 is considered elevated.
Possible Causes and Recommendations
- Dehydration: increase fluid intake to 2-3 liters of water daily unless contraindicated by other medical conditions 1.
- Decreased kidney perfusion: review current medications with your healthcare provider, as certain medications like NSAIDs, ACE inhibitors, and diuretics can affect this ratio.
- Increased protein breakdown: consider dietary changes and consult with a healthcare provider or a registered dietitian.
Importance of Accurate Measurement
Accurate measurement of the change in BUN concentration is crucial, and blood samples must be collected properly, taking into account the site of the blood draw, needle or catheter preparation, blood and dialysate pump flow rates, ultrafiltration rate, and the timing of the blood sampling with respect to the initiation and completion of hemodialysis 1.
Next Steps
If you're experiencing symptoms like fatigue, dizziness, or decreased urination, seek medical attention promptly. Your provider may recommend additional tests like complete metabolic panel, urinalysis, or kidney imaging to determine the underlying cause. This finding warrants follow-up with your healthcare provider, especially if you have existing kidney disease, heart failure, or liver disease.
From the Research
Significance of Elevated BUN to Creatinine Ratio
- An elevated Blood Urea Nitrogen (BUN) to Creatinine (Creat) ratio has been traditionally associated with prerenal azotemia, which is suggested to have a better prognosis than other forms of acute kidney injury (AKI) 2.
- However, studies have shown that a high BUN to Creatinine ratio is associated with increased mortality in critically ill patients, and it is not a reliable parameter for distinguishing prerenal AKI from intrinsic AKI 2, 3.
- The BUN to Creatinine ratio is affected by many renal and nonrenal factors, and it is not a sensitive or specific marker for the diagnosis of AKI 4.
- A high urea-to-creatinine ratio has been found to predict long-term mortality independent of AKI among patients hospitalized with an infection, and it identifies a group of patients with a similar long-term mortality risk as patients with persistent AKI 5.
- The use of the BUN to Creatinine ratio as a diagnostic tool is limited, and it should not be employed to predict prerenal azotemia or to classify AKI in critically ill patients 2, 3.