BUN 57 mg/dL
= 20.35 mmol/L in SI units
Contact your doctor promptly to discuss this result.
- Low
- Slightly low
- Normal
- Slightly high
- High
- Markedly high
- Severely high
- Critically high
At a glance
- Your band
- Markedly high · 45–6 mg/dL
- Distance from typical range
- 33 mg/dL above 24
- SI units
- 57 mg/dL = 20.35 mmol/L
What 57 mg/dL means
A BUN of 57 mg/dL is markedly elevated — roughly two to two-and-a-half times the upper limit of the typical adult range of about 6–24 mg/dL.
A BUN in this range usually signals a significant problem such as substantial kidney impairment, severe dehydration, bleeding in the digestive tract, or a blocked urinary system. It needs prompt medical attention — the same day or next day — even though laboratories that define a formal critical (panic) alert for BUN typically set it around 100 mg/dL and above. How urgent it truly is depends on your symptoms, your creatinine, and whether this is new for you; people with known advanced kidney disease sometimes run values here under close medical supervision.
Bands on this page use the 6–24 mg/dL adult reference range cited by Mayo Clinic; many other references and US labs use narrower ranges such as 6–20 or 7–20 mg/dL (MedlinePlus cites 6–20 mg/dL). Most US lab reports use a single adult range rather than separate male and female ranges, though some references (for example Cleveland Clinic: about 6–21 mg/dL for adult women and 8–24 mg/dL for adult men) publish sex-specific values. Where US labs define a formal critical (panic) alert for BUN, it is most often set around 100 mg/dL, with some labs using cutoffs as low as 80 mg/dL; our critically-high band therefore begins at 80 mg/dL, and because this page's scale tops out at 100 mg/dL, any result at or above 100 falls in that band.
Common causes
- Acute kidney injury
- Advanced chronic kidney disease
- Severe dehydration from vomiting, diarrhea, or heat illness
- Significant bleeding in the stomach or intestines
- Blockage of urine flow, such as severe prostate enlargement or an obstructing stone
- Heart failure with poor blood flow to the kidneys
- High-dose corticosteroids combined with another stressor such as infection
Symptoms that can go with it
- Marked fatigue or drowsiness
- Confusion or trouble concentrating
- Nausea, vomiting, or loss of appetite
- Urinating much less than usual, or not at all
- Swelling in the legs, feet, or face
- Muscle cramps or twitching
- Itchy skin
- Black, tarry stools or vomiting blood if the cause is bleeding
Sensible next steps
- Contact your clinician today, or go to an urgent care clinic if you cannot reach them — a result this high should be evaluated promptly, not filed away
- Go to the emergency department now if you are barely urinating, confused, repeatedly vomiting, short of breath, or passing black or bloody stools
- Expect prompt repeat blood work — creatinine, eGFR, and electrolytes such as potassium — plus urine tests and possibly a kidney ultrasound
- Do not start or stop medications on your own, but make sure the evaluating clinician knows about NSAIDs, diuretics, and blood pressure medicines you take
- Bring the printed lab report and any prior results with you so the trend is clear
Frequently asked questions
Is 57 mg/dL a normal BUN level?
No — 57 mg/dL is markedly above the typical adult range of about 6–24 mg/dL, roughly two to two-and-a-half times the upper limit. A result like this needs prompt medical attention, ideally the same day or next day.
What does a high BUN level mean?
At 57 mg/dL, the most likely explanations are significant: substantial kidney impairment, severe dehydration, digestive-tract bleeding, or blocked urine flow. This level calls for prompt evaluation — same day or next day — rather than waiting for a routine appointment.
Can dehydration alone explain a BUN of 57 mg/dL?
Only severe dehydration produces values like 57 mg/dL, and severe dehydration is itself a medical problem. Whether the cause is fluid loss, kidney impairment, or bleeding, a result this high needs prompt evaluation rather than a wait-and-rehydrate approach.
What is a dangerously high BUN level?
Your result of 57 mg/dL is in the range clinicians treat as seriously elevated, even though laboratories that define a formal critical (panic) alert for BUN typically set it around 100 mg/dL and above. It needs same-day or next-day medical attention — and an emergency visit right away if you are barely urinating, confused, vomiting repeatedly, or passing black or bloody stools.
What does a low BUN level mean?
Low BUN usually means the body is making less urea, not that the kidneys are failing — in fact, low values are far less often a medical problem than high ones. Common explanations are a low-protein diet, generous hydration, and pregnancy. The main exception worth knowing about is advanced liver disease, since a struggling liver produces less urea.
How can I lower my BUN level?
That depends entirely on why it is high, so the honest first step is finding the cause with your clinician. If dehydration is the driver, steady fluid intake usually brings BUN down within days. If a very high-protein diet or supplements are contributing, easing back may help. But when the cause is reduced kidney function, heart failure, or bleeding, the underlying condition — not the BUN number — is what needs treatment, and self-directed fixes like forcing fluids or slashing protein can backfire. Never stop a prescribed medication to lower a lab value without medical advice.
Check a different BUN value
Sources
- BUN (Blood Urea Nitrogen) Test — MedlinePlus, US National Library of Medicine
- Blood urea nitrogen (BUN) test — Mayo Clinic
- Blood Urea Nitrogen (BUN) Test — Cleveland Clinic
- BUN and Creatinine — Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition — NCBI Bookshelf, National Library of Medicine
Educational information, not medical advice. Reference ranges vary between labs — always compare with the range printed on your own report and discuss results with your doctor. Full disclaimer