Blood test

High BUN level in the blood

Blood test
High BUN level in the blood

What is high BUN in the blood called?

  • Azotemia

What is the normal BUN level in the blood?

If you need to know which are the BUN reference ranges or you require more information about the role of BUN in the blood you can visit: Normal BUN level in the blood

What does a high BUN level in the blood mean?

A high value of BUN (blood urea nitrogen) in the blood is a sign of kidney disorders.

Besides, a high level of BUN in the blood may be a consequence of a high-protein diet, dehydration, upper gastrointestinal bleeding (from the esophagus, stomach or duodenum) or medication.

BUN high levels can be classified into prerenal or postrenal:

  • Prerenal azotemia is related to dehydration, protein degradation, corticosteroids or decreased renal perfusion.
  • Postrenal azotemia is related to urinary tract obstruction. Creatinine level in the blood will also be high.

BUN values are usually given in mg/dl but sometimes you can see those values in mmol/l following the International System of Units (SI). In case your values are in mmol/l you can convert them using this web

Warning: In Europe and other countries, the values measured are the total urea instead of BUN (Blood urea nitrogen). The formula to convert from BUN to urea is BUN= Urea * 0.4667. You can convert them using this tool.

  • Moderate azotemia (22 – 56 mg/dl in adults):

    The BUN level in the blood is a bit high. The causes can be multiples, dehydration, high intake of proteins or drug interaction.

    You should talk to your doctor. If he considers it appropriate, he may request additional screening tests.

    You should reduce your protein intake (eating less meat and fish) and increase your water intake. Take a new blood test in a few months and it is probable that the BUN values return to normal range.

  • Marked azotemia (56 - 117 mg/dl in adults):

    The BUN level in the blood is very high. It is necessary to study creatinine level in the blood to know if there is a kidney problem.

    A high value of BUN in the blood is usually a sign of decline in kidney function. The kidneys may lose 30 to 60% of their function. You should visit your doctor. He will prescribe you the appropriate treatment and he will decide if additional screening tests are necessary.

  • Severe azotemia (> 117 mg/dl in adults):

    The BUN level in the blood is so high that the first is to suspect of a kidney failure.

    You should visit your doctor as soon as possible. He will decide the best treatment in your circumstances that may include dialysis.

Which factors can raise your BUN level in the blood?

There are some circumstances or drugs than can raise your BUN level in the blood:

  • Protein excess intake
  • Dehydration (due to excessive sweating, vomiting or diarrhea)
  • Metal poisoning
  • Cardiac arrest
  • Upper GI (gastrointestinal) bleeding
  • Hypovolemia (burns, dehydration)
  • Drugs
    • Antibiotics
      • Amphotericin B
      • Cephalosporin B
      • Streptomycin
      • Gentamicin
      • Tetracycline
      • Vancomycin
    • Antineoplastics
      • Methotrexate
    • Antiepileptic drugs
      • Carbamazepine
    • Antituberculars
      • Rifampicin
    • Bacteriostatic agent
      • Chloramphenicol
    • Diuretics
      • Spironolactone
      • Furosemide
      • Thiazides

Which diseases can raise your BUN level in the blood?

There are different diseases why the BUN level in the blood can be higher than normal:

  • Kidney failure
  • Gastroduodenal ulcer
  • Gout
  • Pneumonia
  • Addison's disease
  • Hypochlorhydria
  • Kidney stone disease
  • Hypertensive kidney disease
  • Renal tuberculosis
  • Glomerulonephritis
  • Pyelonephritis
  • Acute tubular necrosis
  • Reye syndrome
  • Diabetic ketoacidosis
  • Diabetic nephropathy
  • Metabolic acidosis
  • Hemolytic-uremic syndrome

What can I do to lower the BUN level in the blood?

If the BUN level in the blood is a bit high, you can consider the following tips:

  • Follow a low-protein diet. You should reduce the intake of meat and fish.
  • Increase the water intake (at least 2 liters everyday)
  • Take a look at the medication you are taking and talk to your doctor if it is necessary.

If the BUN level is too high it may be a sign of kidney failure and it is possible that you require dialysis to remove accumulated toxins from the body.

Where can I find more information about BUN level in the blood?

You can visit our pages about:

Which values are considered a high BUN level in the blood?

The following values are considered to be above the normal range:

IMPORTANT: These levels are expressed in mg/dl. They are an example of a healthy man of about 45 years of age with no known disease, not taking any medication and with an appropriate intake of protein in the diet. The ranges can be different depending on the laboratory or on your personal circumstances.

Moderate azotemia
23 mg/dl24 mg/dl25 mg/dl26 mg/dl27 mg/dl28 mg/dl29 mg/dl30 mg/dl
31 mg/dl32 mg/dl33 mg/dl34 mg/dl35 mg/dl36 mg/dl37 mg/dl38 mg/dl
39 mg/dl40 mg/dl41 mg/dl42 mg/dl43 mg/dl44 mg/dl45 mg/dl46 mg/dl
47 mg/dl48 mg/dl49 mg/dl50 mg/dl51 mg/dl52 mg/dl53 mg/dl54 mg/dl
55 mg/dl56 mg/dl      
Marked azotemia
57 mg/dl58 mg/dl59 mg/dl60 mg/dl61 mg/dl62 mg/dl63 mg/dl64 mg/dl
65 mg/dl66 mg/dl67 mg/dl68 mg/dl69 mg/dl70 mg/dl71 mg/dl72 mg/dl
73 mg/dl74 mg/dl75 mg/dl76 mg/dl77 mg/dl78 mg/dl79 mg/dl80 mg/dl
81 mg/dl82 mg/dl83 mg/dl84 mg/dl85 mg/dl86 mg/dl87 mg/dl88 mg/dl
89 mg/dl90 mg/dl91 mg/dl92 mg/dl93 mg/dl94 mg/dl95 mg/dl96 mg/dl
97 mg/dl98 mg/dl99 mg/dl100 mg/dl101 mg/dl102 mg/dl103 mg/dl104 mg/dl
105 mg/dl106 mg/dl107 mg/dl108 mg/dl109 mg/dl110 mg/dl111 mg/dl112 mg/dl
113 mg/dl114 mg/dl115 mg/dl116 mg/dl117 mg/dl   
Severe azotemia
118 mg/dl119 mg/dl120 mg/dl121 mg/dl122 mg/dl123 mg/dl124 mg/dl125 mg/dl
126 mg/dl127 mg/dl128 mg/dl129 mg/dl130 mg/dl131 mg/dl132 mg/dl133 mg/dl
134 mg/dl135 mg/dl136 mg/dl137 mg/dl138 mg/dl139 mg/dl140 mg/dl141 mg/dl
142 mg/dl143 mg/dl144 mg/dl145 mg/dl146 mg/dl147 mg/dl148 mg/dl149 mg/dl
150 mg/dl151 mg/dl152 mg/dl153 mg/dl154 mg/dl155 mg/dl156 mg/dl157 mg/dl
158 mg/dl159 mg/dl160 mg/dl161 mg/dl162 mg/dl163 mg/dl164 mg/dl165 mg/dl
166 mg/dl167 mg/dl168 mg/dl169 mg/dl170 mg/dl171 mg/dl172 mg/dl173 mg/dl
174 mg/dl175 mg/dl176 mg/dl177 mg/dl178 mg/dl179 mg/dl180 mg/dl181 mg/dl
182 mg/dl183 mg/dl184 mg/dl185 mg/dl186 mg/dl187 mg/dl188 mg/dl189 mg/dl
190 mg/dl191 mg/dl192 mg/dl193 mg/dl194 mg/dl195 mg/dl196 mg/dl197 mg/dl
198 mg/dl199 mg/dl200 mg/dl201 mg/dl202 mg/dl203 mg/dl204 mg/dl205 mg/dl
206 mg/dl207 mg/dl208 mg/dl209 mg/dl210 mg/dl211 mg/dl212 mg/dl213 mg/dl
214 mg/dl215 mg/dl216 mg/dl217 mg/dl218 mg/dl219 mg/dl220 mg/dl221 mg/dl
222 mg/dl223 mg/dl224 mg/dl225 mg/dl226 mg/dl227 mg/dl228 mg/dl229 mg/dl
230 mg/dl231 mg/dl232 mg/dl233 mg/dl234 mg/dl235 mg/dl236 mg/dl237 mg/dl
238 mg/dl239 mg/dl240 mg/dl241 mg/dl242 mg/dl243 mg/dl244 mg/dl245 mg/dl
246 mg/dl247 mg/dl248 mg/dl249 mg/dl250 mg/dl251 mg/dl252 mg/dl253 mg/dl
254 mg/dl255 mg/dl256 mg/dl257 mg/dl258 mg/dl259 mg/dl260 mg/dl261 mg/dl
262 mg/dl263 mg/dl264 mg/dl265 mg/dl266 mg/dl267 mg/dl268 mg/dl269 mg/dl
270 mg/dl271 mg/dl272 mg/dl273 mg/dl274 mg/dl275 mg/dl276 mg/dl277 mg/dl
278 mg/dl279 mg/dl280 mg/dl281 mg/dl282 mg/dl283 mg/dl284 mg/dl285 mg/dl
286 mg/dl287 mg/dl288 mg/dl289 mg/dl290 mg/dl291 mg/dl292 mg/dl293 mg/dl
294 mg/dl295 mg/dl296 mg/dl297 mg/dl298 mg/dl299 mg/dl300 mg/dl301 mg/dl
302 mg/dl303 mg/dl304 mg/dl305 mg/dl306 mg/dl307 mg/dl308 mg/dl309 mg/dl
310 mg/dl311 mg/dl312 mg/dl313 mg/dl314 mg/dl315 mg/dl316 mg/dl317 mg/dl
318 mg/dl319 mg/dl320 mg/dl321 mg/dl322 mg/dl323 mg/dl324 mg/dl325 mg/dl
326 mg/dl327 mg/dl328 mg/dl329 mg/dl330 mg/dl331 mg/dl332 mg/dl333 mg/dl
334 mg/dl335 mg/dl336 mg/dl337 mg/dl338 mg/dl339 mg/dl340 mg/dl341 mg/dl
342 mg/dl343 mg/dl344 mg/dl345 mg/dl346 mg/dl347 mg/dl348 mg/dl349 mg/dl
350 mg/dl351 mg/dl352 mg/dl353 mg/dl354 mg/dl355 mg/dl356 mg/dl357 mg/dl
358 mg/dl359 mg/dl360 mg/dl361 mg/dl362 mg/dl363 mg/dl364 mg/dl365 mg/dl
366 mg/dl367 mg/dl368 mg/dl369 mg/dl370 mg/dl371 mg/dl372 mg/dl373 mg/dl
374 mg/dl375 mg/dl376 mg/dl377 mg/dl378 mg/dl379 mg/dl380 mg/dl381 mg/dl
382 mg/dl383 mg/dl384 mg/dl385 mg/dl386 mg/dl387 mg/dl388 mg/dl389 mg/dl
390 mg/dl391 mg/dl392 mg/dl393 mg/dl394 mg/dl395 mg/dl396 mg/dl397 mg/dl
398 mg/dl399 mg/dl400 mg/dl401 mg/dl402 mg/dl403 mg/dl404 mg/dl405 mg/dl
406 mg/dl407 mg/dl408 mg/dl409 mg/dl410 mg/dl411 mg/dl412 mg/dl413 mg/dl
414 mg/dl415 mg/dl416 mg/dl417 mg/dl418 mg/dl419 mg/dl420 mg/dl421 mg/dl
422 mg/dl423 mg/dl424 mg/dl425 mg/dl426 mg/dl427 mg/dl428 mg/dl429 mg/dl
430 mg/dl431 mg/dl432 mg/dl433 mg/dl434 mg/dl435 mg/dl436 mg/dl437 mg/dl
438 mg/dl439 mg/dl440 mg/dl441 mg/dl442 mg/dl443 mg/dl444 mg/dl445 mg/dl
446 mg/dl447 mg/dl448 mg/dl449 mg/dl450 mg/dl451 mg/dl452 mg/dl453 mg/dl
454 mg/dl455 mg/dl456 mg/dl457 mg/dl458 mg/dl459 mg/dl460 mg/dl461 mg/dl
462 mg/dl463 mg/dl464 mg/dl465 mg/dl466 mg/dl467 mg/dl468 mg/dl469 mg/dl
470 mg/dl471 mg/dl472 mg/dl473 mg/dl474 mg/dl475 mg/dl476 mg/dl477 mg/dl
478 mg/dl479 mg/dl480 mg/dl481 mg/dl482 mg/dl483 mg/dl484 mg/dl485 mg/dl
486 mg/dl487 mg/dl488 mg/dl489 mg/dl490 mg/dl491 mg/dl492 mg/dl493 mg/dl
494 mg/dl495 mg/dl496 mg/dl497 mg/dl498 mg/dl499 mg/dl500 mg/dl 
foto de Dr. Javier Muga Bustamante
Written by

Dr. Javier Muga Bustamante

Last update: 27/04/2020


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  • Lab Test: Blood Urea Nitrogen, BUN Level. Disponible en:

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