Your blood urea nitrogen (BUN) levels provide valuable information about your kidneys that help diagnose diseases such as uremia and CKD. Test values beyond 20 mg/dL in a BUN test are considered abnormal and can be due to various factors.
📅 Last Updated: April 2026 | 🩺 Medically Reviewed by: Edward Salko, D.O., Medical Director | 🧪 Lab Partner: Labcorp
However, a dangerously high BUN level, often starting from 50 mg/dL, indicates kidney damage that should be addressed immediately. If you have a BUN between 100 mg/dL to 250 mg/dL, it could be due to severe kidney dysfunction, specifically involving its ability to filter waste products.
BUN Level Reference Table
| BUN Level | Classification | What It Means |
|—|—|—|
| 6–20 mg/dL | Normal | Kidneys filtering waste properly |
| 21–50 mg/dL | Elevated | Possible dehydration, high protein diet, or early kidney stress |
| 50–100 mg/dL | High | Significant kidney impairment — medical evaluation needed |
| 100–250 mg/dL | Dangerously High | Severe kidney dysfunction — dialysis may be required |
| Above 250 mg/dL | Critical | Kidney failure — emergency care required |
The BUN/Creatinine Ratio — Why It Matters More Than BUN Alone
A single BUN reading tells you something is off — but the
BUN/Creatinine ratio tells you why. Creatinine is another
waste product filtered by the kidneys. When both BUN and
creatinine are elevated together, it strongly points to
kidney disease. When BUN is high but creatinine is normal,
it usually points to dehydration or high protein intake
rather than kidney damage.
Normal BUN/Creatinine ratio: 10:1 to 20:1
Above 20:1 — suggests pre-renal causes: dehydration,
high protein diet, gastrointestinal bleeding, or heart failure
Below 10:1 — suggests post-renal or intrinsic kidney disease,
malnutrition, or liver disease
Above 40:1 — strongly suggests acute upper gastrointestinal
bleeding or severe dehydration
This is why the Comprehensive Metabolic Panel (CMP) is the
preferred test for evaluating BUN — it measures both BUN and
creatinine simultaneously in a single blood draw, giving you
the ratio your doctor uses to determine the actual cause.
Did You Know? You can take a BUN test as an independent lab test. But it is also usually included in test panels along with other blood tests that check your overall health, like the CMP 14 blood test.
What Is a Blood Urea Nitrogen (BUN) Blood Test?
Your doctor may ask for a blood urea nitrogen or BUN test as part of the lab work for assessing your kidney function. Specifically, a BUN test measures the amount of urea nitrogen in the blood.
Urea nitrogen is a chemical waste product that the kidneys remove from the body. If this is not the case, you could be experiencing conditions like dehydration, urinary tract obstruction, or gastrointestinal bleeding.
While BUN levels reveal critical information about your renal function, it does not warrant a direct diagnosis of any condition unless taken without the other kidney function tests.
What Bun Level Is Too High
Normal BUN levels should be between 6 to 20 milligrams per deciliter (mg/dL). Beyond the upper limit (>20 mg/dL), your BUN level is considered abnormally high.
Symptoms of High BUN Level
If your doctor suspects kidney disease, a BUN test, together with other related tests, will be requested. This can be determined by symptoms of kidney disease, which include the following:
- Frequent urination
- Discolored urine
- Extreme fatigue
- Skin itching
- Muscle cramps
- Restless legs
- Joint and bone pain
- Swelling in hand and feet
High BUN Causes
High BUN levels indicate various medical conditions and may suggest certain lifestyle adjustments. While a BUN test helps diagnose certain diseases, especially revolving around kidney function, it can also highlight imbalances or injuries affecting blood circulation in the renal area.
Dehydration
While elevated BUN is often associated with kidney function impairment, it’s also possible that it could be due to chronic dehydration.
Water plays a crucial role in waste removal – via urination, perspiration, or defecation – as it dilutes the chemical byproducts. As a result, when you’re dehydrated, BUN increases as fluid volume is low.
In addition, creatinine (another waste product) gets altered with dehydration. Typically, your BUN/creatinine ratio should be about 10:1 or 20:1.
Lack of water in your body will drive these numbers higher as blood flow to the kidneys gets reduced. This makes it an ideal parameter for risk prediction among patients in the emergency department.
High Protein Diet
Dietary nitrogen mainly comes from protein. Therefore, a diet that constitutes high protein sources, like red meat, beans, fish, etc., increases your BUN significantly. In the same way, a high protein diet also elevates creatinine, tipping off the ratio for your BUN/creatinine.
People who are bulking up and consume protein shakes are also at risk of having high BUN. Typically, a change in diet fixes this condition unless other factors play in.
Medical Disorders (Renal Failure)
High BUN suggests kidney problems that prohibit proper function, such as in glomerular filtration. Thus, it’s often tied up with chronic kidney disease (CKD) and uremia.
However, it could also be due to other disorders linked to decreased blood flow or volume directed toward the kidneys. These include gastrointestinal bleeding, congestive heart failure, urinary tract obstruction, diabetes mellitus, Addison’s disease, and severe burns.
Certain Medications
Elevated BUN may not be due to any disease or medical condition. Sometimes, it can be a side effect of specific medications prescribed by your doctor. It could be from taking any of the following:
- Rifampin
- Tetracycline
- Vancomycin
- Methotrexate
- Amphotericin
- Spironolactone
- Carbamazepine
High-intensity Workouts
Vigorous exercises, such as resistance and strength training, can cause damage to the muscle tissues, which increases biomarkers for kidney disease. Hence, it’s highly likely that your high BUN can be linked to constant muscle injury if you regularly engage in high-intensity workouts.
On top of this, those who spend most of their time in the gym, doing strenuous exercises, are also constantly subjected to dehydration and high protein intake. If these routines are left unchecked, they could become compounded factors for elevated BUN.
Constant “fight or flight” response activation
When your sympathetic nervous system or “fight or flight” response is activated regularly, it leads to activities that can raise your BUN.
For example, your cortisol (stress hormone) increases and breaks down more protein than average. Your blood circulation also gets altered, affecting the transport of waste products to the urinary system. These result in the accumulation of BUN in the kidney.
Common triggers of the “fight or flight” response are stress, anxiety, and shock. So if you’re frequently experiencing these events, make sure to have your kidney functions tested. And, of course, employ the necessary lifestyle adjustments to avoid stress.
How To Lower Bun Levels? 4 Ways to Do It
The right action toward lowering your BUN levels depends on what’s causing the condition. While high BUN may suggest health conditions affecting your kidney, it could also be due to other factors you can correct within your means – most notably dehydration and an unbalanced protein diet. In other cases, it can be due to age-related disorders, which you can openly discuss with your healthcare provider.
Nevertheless, here are some practical ways to lower BUN levels.
- Increase Your Water Intake
If the high BUN level you got from your blood test is traced back to dehydration, it only makes sense to increase your water intake. Unfortunately, people often overlook their daily hydration due to a tight schedule or simply because it was not established in their routine.
You can use apps that remind you to drink water or keep a bottle nearby. At first, you’ll find yourself visiting the restroom frequently, but you’ll get used to it as your body start to adjust.
How much water you should drink daily will depend on factors such as your body size, age, and kidney health, as well as environmental conditions like the climate in your area. This means the standard eight glasses of water a day may not necessarily apply to you. Hence, consult with your doctor.
Additionally, you can track the changes in your hydration – and by extension, your kidney function – when you check your urine color. For example, healthy urine often has a yellow to deep-amber color. In the same way, how your urine smells also provides hints about your kidney function and whether or not you should hydrate more.
- Limit Protein-Rich Foods
Cutting back on your protein intake can make a significant difference in your BUN levels, especially if it is the primary trigger. As too much protein can make the kidneys work twice as hard, protein-rich foods are often controlled in renal diets for those with kidney disease.
Limit your intake of red meat, fish, dairy, beans, seeds, and shellfish. Likewise, if you have been taking protein powder shakes, you will have to avoid them until your BUN normalizes or as recommended by your doctor.
On top of regulating protein in your diet, consume more kidney-friendly fruits and vegetables. These include cauliflower, cranberries, red grapes, bell peppers, olive oil, and cabbage.
- Manage Your Stress
When you are constantly subjected to stress, you activate your “fight or flight response,” which alters your blood and organ activities, affecting your BUN levels. Therefore, effective stress management does not only benefit your kidney health but your overall physical and mental wellness as well.
However, make sure to avoid common mistakes when controlling stress, like binge eating or oversleeping, as these could aggravate the condition instead of alleviating it. Know more about the unhealthy ways of coping with stress.
Instead, lean more toward these practical ways to manage stress, which may help lower BUN levels.
- Breathing exercises
- Meditation and yoga
- Listening to calming music
- Picking up a hobby
- Building a work-life balance
- Doing light exercises
- Getting enough sleep
- Eating a balanced diet
- Avoiding alcohol and stimulants
- Spending time with family and friends
Paying more attention to your holistic wellness often helps lower your stress. Check out some of the best self-care activities you can do over the weekend to help reset and maintain optimum kidney health.
- Avoid Extensive Exercise
Working out too much brings your BUN on the upper scale. Your doctor may recommend reducing your exercise intensity to help your kidneys function better.
You may be tempted to withdraw from getting physical altogether, but this might cause more damage than help. So, instead, opt for light exercises within shorter time periods. Rather than heavy workouts, you can focus more on doing cardio exercises that don’t require too much work, such as walking and low-impact aerobics.
You can also consider engaging in recreational activities that are not too physically demanding but equally fun, like water aerobics and calisthenics. Whichever activity you choose, the rule of thumb is that it shouldn’t have high intensity.
Check Your BUN and Kidney Function — No Doctor Visit Needed
The fastest way to know if your BUN is elevated and what is
causing it is a Comprehensive Metabolic Panel (CMP) — which
measures BUN, creatinine, BUN/creatinine ratio, electrolytes,
liver enzymes, and glucose in a single blood draw at any
Labcorp location. Order online, visit any of 4,000+ Labcorp
patient service centers nationwide, and get results in 24–48
hours. HSA and FSA eligible. No doctor visit or referral required.
Frequently Asked Questions: High BUN Levels
What is a dangerous BUN level?
A BUN level above 50 mg/dL is considered high and indicates significant kidney impairment requiring medical evaluation. BUN between 100 and 250 mg/dL indicates severe kidney dysfunction where dialysis may be necessary. Above 250 mg/dL is a medical emergency. Normal BUN ranges from 6 to 20 mg/dL in most adults.
What causes high BUN levels?
The most common causes of elevated BUN are dehydration, a high-protein diet, kidney disease, heart failure, gastrointestinal bleeding, and certain medications. BUN can also be temporarily elevated after intense exercise. The BUN/creatinine ratio helps distinguish kidney disease (both elevated) from dehydration or high protein intake (BUN high, creatinine normal).
What is a normal BUN/creatinine ratio?
A normal BUN/creatinine ratio is between 10:1 and 20:1. A ratio above 20:1 typically suggests pre-renal causes like dehydration or gastrointestinal bleeding. A ratio below 10:1 may suggest kidney disease, malnutrition, or liver disease. A ratio above 40:1 strongly suggests acute upper gastrointestinal bleeding or severe dehydration.
How can I lower my BUN levels naturally?
For BUN elevated by dehydration — increase water intake to at least 8-10 glasses daily. For BUN elevated by high protein diet — reduce red meat, poultry, and dairy and increase fruits and vegetables. For BUN elevated by stress — implement stress management strategies as cortisol directly affects kidney filtration. For BUN elevated by excessive exercise — reduce workout intensity and increase hydration. BUN caused by kidney disease requires medical treatment beyond lifestyle changes.
What blood test checks BUN levels?
BUN is included in the Comprehensive Metabolic Panel (CMP) — a 14-marker panel that also measures creatinine, electrolytes, liver enzymes, and glucose in a single blood draw. The CMP is the standard test for evaluating kidney function and is available through Personalabs without a doctor’s visit. Order online, visit any Labcorp location, and get results in 24 to 48 hours.
The Bottom Line
Getting a high BUN level, whether in your diagnostic test or routine basic metabolic panel eight blood test, can be due to a lifestyle mishap or a budding kidney disease. Either way, you must let your doctor know as soon as possible. Understanding high BUN levels not only allows for accurate treatment but also routine changes that will keep your kidneys healthy and well-functioning.