BUN to creatinine ratio is a medical laboratory test that measures the ratio of two substances in the blood: Blood Urea Nitrogen (BUN) and Creatinine. These two values are commonly used to evaluate kidney function and to differentiate between various causes of acute or chronic kidney injury.
| Also Known as | BUN to Creatinine ratio, Blood Urea Nitrogen to Creatinine Ratio, BUN / Creatinine Ratio |
| Test Purpose | 1. To find the cause of azotemia or renal failure. 2. It will differentiate prerenal and postrenal azotemia from renal azotemia. 3. BUN/Creatinine ratio is a rough guide for renal disease. |
| Test Preparations | No Preparation Needed |
| Test Components | Blood Urea Serum Creatinine |
| Specimen | 2 ML (0.5 ML Min.) Serum From 1 SST. Ship Refrigerated Or Frozen. |
| Stability Room | 2 Hours |
| Stability Refrigerated | 1 Week |
| Stability Frozen | 2 Weeks |
| Method | R. Chemistry |
| Download Report | Download Report |
Definations:
BUN to Creatinine Ratio:
The BUN to Creatinine Ratio is a medical test that compares the levels of blood urea nitrogen (BUN) and creatinine in the blood to assess kidney function and detect certain kidney-related conditions.
BUN (Blood Urea Nitrogen):
BUN (Blood Urea Nitrogen) is a medical test that measures the amount of urea nitrogen in the blood, which is a waste product produced when the body breaks down proteins. It is used to assess kidney function and diagnose various kidney and liver-related conditions.
Creatinine:
Creatinine is a waste product that is produced by the muscles during normal metabolism. It is filtered out of the blood by the kidneys and excreted in the urine. Measuring creatinine levels in the blood helps evaluate kidney function and diagnose kidney diseases or impairments.
Results Meaning:
| BUN/creatinine >20 | BUN/creatinine <10 |
|---|---|
| dehydration | acute tubular necrosis |
| hypovolemia | liver disease |
| shock, heart attack, severe burns | malnutrition |
| congestive heart failure | pregnancy |
| very high protein intake | SIADH (syndrome of inappropriate antidiuretic hormone) |
| gastrointestinal bleeding | rhabdomyolysis |
| advanced age |
Why get tested?
To assess the health of your kidneys; to help diagnose kidney disease; to monitor the effectiveness of dialysis and other treatments related to kidney disease or damage
When to get tested?
As part of a routine basic or comprehensive metabolic panel (CMP or BMP) during a health exam; when you have signs and symptoms that may be due to kidney disease or have a condition that may be caused or worsened by kidney dysfunction; at regular intervals when you are being treated for kidney disease or damage
Sample required?
- 2 ML (0.5 ML Min.) Serum From 1 SST. Ship Refrigerated Or Frozen.
- Estimate serum BUN and Creatinine.
Is preparation needed for the Sample?
None
BUN / Creatinine Ratio Formula:
Serum BUN (mg/dl) / Creatinine (mg/dl)
Normal Values BUN/creatinine ratio :
- BUN/Creatinine ratio = 10 :1
- On normal diet = 12 to 16
- Optimum adult level = 15.5
Ratio is maintained when BUN and creatinine are raised:
- This is suggestive of renal diseases like:
- Intrarenal glomerulonephritis.
- Tubulointerstitial nephritis.
- This is referred to as renal azotemia.
Increased ratio >10:1 while creatinine is normal:
Prerenal azotemia, where BUN rises without the increase in creatinine, is due to decreased GFR and is seen in:
- Heart failure.
- Dehydration.
- Blood loss.
- Salt depletion.
- GI tract hemorrhage.
- High protein intake.
- Certain drugs like tetracycline and glucosteroids.
Increased ratio = >10:1 with raised creatinine level is seen in:
Postrenal azotemia where BUN rises without any ratio to creatinine increase.
- Obstructive uropathy.
- Prerenal azotemia is superimposed on renal disease.
Decreased Ration <10:1 with decreased BUN value is seen in:
- Acute tubular necrosis.
- Starvation.
- Low-protein diet.
- Severe liver disease.
- Any etiology leading to decreased synthesis of urea.
- Repeated dialysis.
- Pregnancy.
Decreased Ratio <10:1 with increased creatinine level is seen in:
- Rhabdomyolysis (There is the release of muscle creatinine).
- Drugs like phenacemide therapy (Will increase the conversion of creatine to creatinine).
- Patients with a muscular body develop renal failure.
BUN : Creatinine Ratio
| Blood Urea Nitroge : Creatinine 20 : 1 | Normal = 12-20 (optimum 15) |
BUN : Creatinine Ratio
| Low | High | High with Raised Creatinine |
|---|---|---|
| Acute tubular necrosis Low-protein Intake Starvation Severe liver disease | Pre-Renal Ureamia High-protein Intake After GI Bleeding | Post-Renal Obstruction Pre-Renal Ureamia with Renal Disease |
Extrarenal Factors Affecting BUN and sCr :
| Factor by mechanism | BUN | sCr |
|---|---|---|
| Increased substrate | ||
| High protein intake | ↑ | → or sl ↑ |
| Gastrointestinal bleeding | ↑ | → |
| Catabolic states (fever, steroids, burns, etc.) | ↑ | → |
| Rhabdomyolysis | ↑ | ↑↑ |
| Decreased substrate | ||
| Malnutrition | ↓ | → |
| Starvation | ↓ | → |
| Hypoperfusion | ||
| Dehydration | ↑ | → |
| Congestive heart failure | ↑ | → |
| Shock | ↑ | → |
| Diminished blood volume (GI bleeding) | ↑ | → |
| Urinary tract obstruction | ↑ | → |
Factors that increase BUN:
- Increased protein in the diet. Low BUN levels may mean you’re not getting enough protein. If this is the case, try increasing your intake of high-protein foods like lean meats and beans.
- Reduce alcohol consumption. Alcohol blocks the production of urea (BUN)
Factors that decrease the BUN:
- Drink more water. Make sure you are well hydrated.
- Lose weight if you are overweight. A high BMI can cause kidney dysfunction and increase BUN (urea) levels.
Factors that increase creatinine:
- Increase physical activity (unless not recommended due to an existing medical condition): Exercise increases creatinine levels and helps build muscle.
- Avoid alcohol. May decrease blood creatinine.
Factors that Decrease creatinine:
- Avoid creatine and creatine-based supplements
- Increase dietary fiber. Fiber from fruits and vegetables improves kidney health and can lower blood creatinine levels.
- Lose some weight if you are overweight. Weight loss can improve the health of your kidneys and lower creatinine levels.
Possible References Used
