Azotemia: What It Is, Why Waste Builds Up in Your Blood, and How It's Treated
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 13, 2026. This content is for educational purposes and is not medical advice.
Quick Answer
Azotemia is a condition in which too much nitrogen, creatinine and other waste builds up in the blood because the kidneys cannot clear it [1]. It is common, involved in about 16% of hospital admissions [1]. Its 3 types are prerenal, intrinsic and postrenal [1]. It often causes no symptoms at first, and treatment depends on the type and cause [1].
What the research says
Caught early, the low-blood-flow kind can be reversed quickly. A nephrology review of kidney injury caused by poor blood flow to the kidneys, abdominal pressure, or urinary blockage explains that with early recognition and correction of the underlying problem, the injury can be reversed rapidly, but the longer or more severe it gets, the more kidney cells are damaged, leading to a longer illness with higher illness and death rates (Molitoris, Clin J Am Soc Nephrol, 2022) [6].
Prerenal azotemia is one of the most common problems in everyday primary care. A primary care review lists prerenal azotemia, along with abnormal sodium and potassium levels, among the most common abnormalities seen in outpatient practice, and notes that volume and electrolyte problems can lead to serious organ dysfunction (Martinez et al., Prim Care, 2020) [7].
What Is Azotemia?
Azotemia happens when waste product levels in your blood are too high, specifically too much nitrogen and other waste products [1]. These waste products form when your body breaks down protein from the foods and drinks you consume [1]. They are created in your liver, travel through your bloodstream to your kidneys, and in a healthy body the kidneys filter them out. The filtered waste then leaves your body through your urine [1] [3].
Think of your kidneys as your body's wastewater treatment plant. Azotemia is what happens when the plant is overloaded, under-supplied, or clogged. The waste stays in the bloodstream instead of being flushed out.
A key fact about azotemia: it often stays completely silent. Many people notice no symptoms until the condition reaches a later stage [1], and some people have no signs at any stage at all. In these cases, a healthcare provider may discover it during testing for something else entirely [1].
How Common Is Azotemia?
Azotemia is common. It accounts for about 16% of hospital admissions [1]. Anyone can get it, but you are more likely to develop it if you are 65 or older [1].
What Are the Types of Azotemia?
Azotemia has three types, each starting with a different problem in the kidney's work chain: blood supply, kidney tissue or drainage.
Type | What Goes Wrong | Common Causes |
Prerenal azotemia | Not enough blood flowing through the kidneys | Blood loss, dehydration, heart failure, liver failure, some medicines (including ibuprofen and aspirin) |
Intrinsic azotemia | Damage to the kidney's own structures | Infection, sepsis, blood clots, certain medications (including chemotherapy drugs), toxins such as drugs and alcohol |
Postrenal azotemia | A blockage in the urinary tract, often in the ureters (the muscle tubes between kidneys and bladder) | Urinary tract infections (UTIs), ureteral stones, some forms of cancer |
Is Azotemia the Same as Kidney Failure, Dehydration, or Uremia?
Azotemia, kidney failure, dehydration and uremia sound similar, but these four terms mean different things. The table below clears up the confusion.
Term | What It Means |
Azotemia | Too much nitrogen and other waste products in your blood |
Kidney (renal) failure | Kidneys stop working properly; this is the main cause of azotemia. They are related but not the same |
Dehydration | Not enough water in your body; a common cause of prerenal azotemia, but not azotemia itself |
Uremia | A dangerous buildup of urea (a type of nitrogen waste) in your blood; azotemia can progress to uremia, which can be fatal without treatment |
What Are the Symptoms of Azotemia?
Because azotemia often has no early warning signs, the symptoms below usually appear only at a later stage.
Symptom | What You May Notice |
Reduced urination | Not peeing a lot |
Fatigue | Feeling very tired |
Confusion | Feeling confused |
Nausea and vomiting | Digestive upset |
Loss of appetite | Not wanting to eat |
Shortness of breath (dyspnea) | Feeling out of breath |
Chest pain | Pain in the chest |
Swelling (edema) | Especially in the legs, ankles, and feet |
Abnormal heartbeat (arrhythmia) | The heart beats irregularly |
Severe azotemia can cause seizures or coma [1]. These are medical emergencies.
What Causes Azotemia?
The cause depends on the type you have.
Prerenal azotemia usually develops from an injury or condition that affects how blood flows to your kidneys. Causes include dehydration, blood loss from a damaged blood vessel (hemorrhage), burns, heart failure, and liver failure [1].
Intrinsic azotemia develops after damage to the kidney's structures: the tiny filters called glomeruli that remove waste, the small renal tubules that reabsorb water, nutrients, and minerals, and the renal vasculature (the arteries and veins in your kidneys) [1] [3]. Conditions that cause inflammation, including vasculitis and infections, often cause intrinsic azotemia [1]. Toxins can also cause it, as can damage from low blood flow (hypoperfusion) [1].
Postrenal azotemia is usually caused by blockages in your ureters and/or bladder [1]. Risk factors include UTIs, ureteral stones, swollen kidneys (hydronephrosis), and an enlarged prostate (benign prostatic hyperplasia) [1].
Type | Why It Happens |
Prerenal | Something cuts the blood supply to the kidneys: dehydration, bleeding, heart or liver failure, burns |
Intrinsic | The kidney's filters, tubes, or blood vessels are damaged: inflammation, infection, sepsis, toxins |
Postrenal | Pee cannot drain: a blockage in the ureters or bladder stops waste from leaving the body |
What Are the Complications of Azotemia?
Azotemia can lead to a dangerous buildup of waste products in your blood called uremia [1]. Uremia often results from chronic kidney disease (CKD) [1]. Without treatment, uremia can be fatal [1]. That is why taking azotemia seriously, even when you feel fine, matters.
How Is Azotemia Diagnosed?
A healthcare provider who specializes in kidney conditions (a nephrologist) will review your medical history, ask about your symptoms, and conduct a physical examination. If they suspect azotemia, they will order a blood urea nitrogen (BUN) test and check your creatinine levels [1]. Creatinine is a waste product of muscle tissue metabolism [1].
What BUN Level Indicates Azotemia?
Normal BUN levels vary by age and sex [1]. Levels higher than the ranges below may indicate azotemia.
Age and Sex | Normal BUN Level (mg/dL) |
Children between 1 and 17 | Between 7 and 20 |
Adult males | Between 8 and 24 |
Adult females | Between 6 and 21 |
What Creatinine Level Indicates a Kidney Problem?
Age and Sex | Normal Serum Creatinine Level (mg/dL) |
Children between 1 and 16 | 0.2 to 0.9 |
Adult males | 0.6 to 1.2 |
Adult females | 0.5 to 1.1 |
Healthcare providers do not use BUN alone to determine kidney failure [1]. However, you likely have kidney failure if your BUN and creatinine numbers are higher than your baseline [1].
What Other Tests Will Be Done?
Test | What It Does |
Urinalysis | You provide a urine sample that is examined for its chemical and microscopic elements |
Urine output | Measures how much you pee over 24 hours |
Imaging tests | A CT scan, ultrasound, or other imaging looks at your kidneys up close |
Kidney biopsy | Your provider numbs your skin, inserts a needle to take a small kidney tissue sample, and sends it to a lab for testing |
How Is Azotemia Treated?
Azotemia treatment depends on which type you have, what is causing it and how severe it is [1]. Your provider will run tests to determine the cause, then choose from options such as:
Treatment | What It Does |
IV fluids | Fluids given through your vein to treat dehydration |
Medications | Diuretics (make you pee), adrenergic drugs (have a similar effect as epinephrine), corticosteroids, and plasma volume expanders (replace blood plasma when you lose a lot of blood) |
Ureteral stents | Allow pee to flow from your kidneys to your bladder when a blockage is in the way |
Dialysis | Removes waste products from your blood when the kidneys cannot |
Can Azotemia Be Prevented?
Azotemia prevention starts with several everyday habits that can help protect your kidneys.
Habit | Why It Helps |
Use certain medications sparingly | NSAIDs, some antibiotics (penicillin, sulfonamides), and herbal supplements can damage kidneys if taken too often. Ask a provider about a safe dose |
Treat blood loss | Decreased blood flow to the kidneys causes prerenal azotemia; apply pressure and bandage wounds, and seek medical attention for serious injuries |
Get screened for kidney disease | A good idea if you have a family history of kidney disease |
Prevent dehydration | Most adults need about eight glasses of water per day; your pee should be clear or pale yellow |
Drink alcohol in moderation | Alcohol damages kidneys, affects filtering, and causes dehydration. Women: one drink or less; men: two drinks or less |
Eat a kidney-healthy diet | Fruits, vegetables, and whole grains; limit salt, since high sodium raises your risk of stones |
Exercise regularly | At least 30 minutes, five to seven days per week |
Quit smoking | Smoking damages blood vessels, which affects blood flow to your kidneys |
What Is the Outlook After Treatment?
With early diagnosis and treatment, the outlook for many people who have azotemia is good [1]. Without treatment, azotemia increases your chances of developing other severe conditions, including chronic kidney disease, and it can also cause death [1]. Following your provider's treatment plan is the best way to reduce those risks.
When Should I Go to the ER?
Go to the emergency room if you notice symptoms of acute kidney failure, which may include not peeing a lot, swelling (especially in the ankles and feet), a metallic taste in your mouth, fatigue, nausea and vomiting, diarrhea, abdominal pain, seizures, or coma [1].
What Questions Should I Ask My Healthcare Provider?
If you have azotemia, you may want to ask: How do I know I have azotemia? What type do I have? Which tests will be ordered? What treatment do you recommend and what are its risks? Is there permanent kidney damage? Should I see a nephrologist?
What is the bottom line on azotemia?
Azotemia is a common, often silent warning sign that your kidneys need help. For many people it causes no symptoms until a late stage, which is why blood tests, not how you feel, usually catch it first. The good news is that the cause is treatable and, with early care, the outlook for many people is good. Your kidneys do the silent work of cleaning your blood every hour of every day; giving them blood flow, water, and reasonable habits is how you keep the treatment plant running.
What first steps can people with azotemia take for kidney health?
You cannot feel your kidneys filtering, but you can protect them. Hydrate regularly, use over-the-counter pain relievers only as directed, and know your numbers: a simple BUN and creatinine check can catch a problem before it starts. Explore Rinnit.com's library of plain-language health guides for more trustworthy answers you can understand in minutes.
Frequently Asked Questions
What are the symptoms of azotemia?
Many people have no symptoms at all. Later-stage signs include peeing less, fatigue, confusion, nausea and vomiting, shortness of breath, chest pain, swelling in the legs, loss of appetite, and abnormal heartbeat. Severe cases can cause seizures or coma.
What causes azotemia?
Three main problems: not enough blood flowing to the kidneys (dehydration, blood loss, heart failure), damage to kidney tissue (infection, sepsis, toxins, certain medications), or a blockage in the urinary tract (UTIs, stones, cancer).
Is azotemia the same as kidney failure?
No. Kidney failure is the main cause of azotemia, but they are not the same condition. Providers do not use BUN alone to diagnose kidney failure.
How is azotemia diagnosed?
A nephrologist orders a BUN test and checks creatinine levels; numbers above the normal range for your age and sex may indicate azotemia. Urinalysis, 24-hour urine output, imaging, and kidney biopsy may follow.
What level of BUN indicates azotemia?
Any level above the normal range (7 to 20 mg/dL for children, 8 to 24 mg/dL for adult males, and 6 to 21 mg/dL for adult females) may indicate azotemia.
How is azotemia treated?
Depending on the type and cause, treatment may include IV fluids, medications (diuretics, corticosteroids, plasma volume expanders), ureteral stents to clear blockages, or dialysis to remove waste from the blood.
Is azotemia contagious?
No. You cannot spread azotemia to another person.
What is the difference between azotemia and uremia?
Azotemia is too much nitrogen and waste products in the blood; uremia is specifically too much urea in the blood and is a dangerous, potentially fatal progression of untreated azotemia.
What is the most common type of azotemia?
Prerenal azotemia, which happens when not enough blood flows through the kidneys.
Can azotemia cause death?
Yes. Without treatment, azotemia can lead to uremia, which can be fatal, and it raises the chance of chronic kidney disease.
Is azotemia the same as dehydration?
No. Dehydration is a common cause of prerenal azotemia, but azotemia refers to the waste buildup in blood, not the water shortage itself.
Who is most likely to get azotemia?
Anyone can get it, but people 65 or older are more likely to develop it.
Can azotemia be prevented?
Steps include preventing dehydration, using certain medications sparingly, treating blood loss promptly, limiting alcohol, quitting smoking, eating a kidney-healthy diet, exercising regularly, and getting screened if kidney disease runs in your family.
When should I go to the ER for azotemia symptoms?
Go immediately for signs of acute kidney failure: peeing very little, significant swelling, a metallic taste in your mouth, seizures, coma, or severe nausea, vomiting, diarrhea, or abdominal pain.
What questions should I ask my healthcare provider?
Ask how they know you have azotemia, what type you have, which tests will be ordered, what treatment is recommended and its risks, whether there is permanent kidney damage, and whether you should see a nephrologist.
Related Reading on Rinnit.com
Chronic Kidney Disease: What It Is, Its 5 Stages, Causes, and How It's Treated: the long-term condition linked to untreated azotemia.
Dehydration: Symptoms, Causes, Risk Groups & Treatment — Complete Guide: the leading cause of prerenal azotemia.
References
Cleveland Clinic. Azotemia. Cleveland Clinic. Last updated May 30, 2023. https://my.clevelandclinic.org/health/diseases/25037-azotemia
Malkina A. Acute Kidney Injury (AKI). Merck Manual Professional Version. Last updated February 2026. https://www.merckmanuals.com/professional/genitourinary-disorders/acute-kidney-injury/acute-kidney-injury-aki
National Institute of Diabetes and Digestive and Kidney Diseases. Your Kidneys & How They Work. NIDDK. Last reviewed June 2018. https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work
Latif W. Prerenal azotemia. MedlinePlus. Reviewed October 28, 2024. https://medlineplus.gov/ency/article/000508.htm
Tyagi A, et al. Azotemia (Archived). In: StatPearls [Internet]. StatPearls Publishing. Last updated May 14, 2023. PMID 30844172. https://www.ncbi.nlm.nih.gov/books/NBK538145/
Molitoris BA. Low-Flow Acute Kidney Injury: The Pathophysiology of Prerenal Azotemia, Abdominal Compartment Syndrome, and Obstructive Uropathy. Clin J Am Soc Nephrol. 2022;17(7):1039-1049. PMID 35584927. https://doi.org/10.2215/CJN.15341121
Martinez LC, et al. Approach to Electrolyte Abnormalities, Prerenal Azotemia, and Fluid Balance. Prim Care. 2020;47(4):555-569. PMID 33121628. https://doi.org/10.1016/j.pop.2020.07.001
Medical disclaimer
This content is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here. If you experience chest pain, shortness of breath, seizures, or coma, call emergency services or go to the nearest emergency room immediately.
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