Quick Verdict
A BUN/creatinine ratio of 10:1-20:1 is normal. Above 20:1 usually means dehydration. Below 10:1 can indicate liver disease. A BMP through HealthLabs gives you both values for $34 — no doctor required.
Quick Answers
- Normal BUN/creatinine ratio: 10:1 to 20:1
- Above 20:1 usually means dehydration
- Below 10:1 can indicate liver disease or muscle breakdown
- BMP test gives both values for $34 at HealthLabs — no doctor required
In This Article
Affiliate disclosure: ReviewPooch earns commission on purchases made through links in this article, at no cost to you.
If your lab results show a flagged BUN/creatinine ratio, here is exactly what it means, what causes it, and whether you need to act on it.
Order BMP at HealthLabs — $34 →What Is the BUN/Creatinine Ratio?
The BUN/creatinine ratio is a calculation your doctor uses to understand why your kidneys might not be working properly. BUN stands for blood urea nitrogen — a waste product your liver makes when it breaks down protein. Creatinine is a waste product from normal muscle activity. Both are filtered out by the kidneys, so when kidney function drops, both numbers rise.
The ratio tells a more specific story than either number alone. A high BUN with normal creatinine points to dehydration or protein overload. High creatinine with normal BUN points to muscle damage or kidney disease. The combination narrows down the cause.
Normal range: 10:1 to 20:1. Most labs flag anything below 10 or above 20 for review.
What Your Result Means
| Ratio | What It Suggests | Common Causes |
|---|---|---|
| Below 10:1 | Low ratio | Liver disease, malnutrition, low protein diet, overhydration |
| 10:1 – 20:1 | Normal | Healthy kidney function |
| 20:1 – 40:1 | High — prerenal | Dehydration, blood loss, heart failure, high protein diet |
| Above 40:1 | Very high — investigate | Severe dehydration, GI bleeding, kidney failure |
High BUN/Creatinine Ratio
A ratio above 20:1 usually means less blood is reaching the kidneys, or there is more protein being broken down than usual.
- Dehydration — the single most common cause. BUN rises faster than creatinine when you are not drinking enough. A ratio of 25-30:1 in an otherwise healthy person who has been sweating or not drinking is almost always dehydration.
- High protein diet — eating a lot of meat or protein supplements increases urea production. Bodybuilders sometimes have ratios of 20-25:1 from diet alone.
- GI bleeding — blood in the digestive tract is digested as protein, which drives BUN up sharply without changing creatinine. A ratio above 30:1 with no other obvious cause warrants investigation.
- Heart failure — when the heart is not pumping efficiently, less blood reaches the kidneys. BUN rises because the kidneys are working harder to concentrate urine.
Low BUN/Creatinine Ratio
A ratio below 10:1 is less common. It means creatinine is elevated relative to BUN, or BUN is lower than expected.
- Liver disease — the liver makes urea from protein. If liver function is impaired, less urea is produced and BUN drops.
- Malnutrition or very low protein diet — less protein means less urea production.
- Rhabdomyolysis — rapid muscle breakdown releases large amounts of creatinine, dropping the ratio sharply.
- Pregnancy — increased blood volume dilutes both values, but creatinine tends to stay lower.
BUN/Creatinine Ratio vs BMP vs CMP
The ratio is not a standalone test — it is calculated from values on a basic metabolic panel (BMP) or full metabolic panel (CMP).
| Test | Includes Ratio | Also Includes | Price at HealthLabs |
|---|---|---|---|
| BUN only | Partial | Nothing else | ~$18 |
| Creatinine only | Partial | Nothing else | ~$18 |
| BMP | Yes | Glucose, electrolytes, CO2 | ~$34 |
| CMP | Yes | BMP + liver enzymes, protein | ~$42 |
If you want the BUN/creatinine ratio, a BMP is the most cost-effective option. It gives you both values plus glucose and electrolytes for around $34.
Do You Need a Doctor to Order This Test?
No. Direct-access lab testing lets you order a BMP yourself without a physician's order. HealthLabs uses the same Quest Diagnostics and LabCorp-certified labs that hospitals use. You skip the $150-300 office visit and get the same result.
This matters if you are monitoring kidney function because of a family history of kidney disease, diabetes, or hypertension. Ordering your own annual BMP is faster and far cheaper than going through your doctor every time.
When Your Results Are Abnormal
A single out-of-range result is rarely a diagnosis on its own. Your hydration when the blood was drawn, recent diet, any medications, and whether you exercised heavily the day before all affect the numbers. Creatinine can run 10-20% higher after a hard workout. BUN can shift 5-10 points based on protein intake.
Certain patterns still warrant follow-up regardless:
- Ratio above 40:1 — see a doctor within days, not weeks
- Creatinine above 1.5 mg/dL (women) or 2.0 mg/dL (men) — kidney function may be impaired
- BUN above 50 mg/dL — investigate GI bleeding or severe dehydration
- Both values elevated with normal ratio — suggests intrinsic kidney disease
Frequently Asked Questions
What is a normal BUN/creatinine ratio?
10:1 to 20:1. Most labs consider anything in this range normal for adults. Athletes and people on high-protein diets sometimes run at the high end (18-22:1) without any underlying disease.
What causes a high BUN/creatinine ratio?
Dehydration is far the most common cause. GI bleeding, high protein intake, heart failure, and severe kidney disease can also raise it. A ratio above 30:1 without an obvious explanation should be investigated.
Can creatine supplements affect the ratio?
Yes. Creatine supplementation increases creatinine production, which lowers the ratio. If you take creatine and your ratio is below 10:1, this is usually the explanation rather than liver disease.
Do I need to fast before a BMP?
Fasting is not required for BUN and creatinine specifically, but HealthLabs recommends fasting 8-12 hours for a full BMP because glucose should be measured fasting for accuracy.
Comparison Table
| Test | Ratio Available | Price (Healthlabs) | Best For |
|---|---|---|---|
| BUN only | No | ~$18 | Quick BUN check only |
| Creatinine only | No | ~$18 | Quick creatinine check |
| BMP | Yes | ~$34 | Full kidney function overview |
| CMP | Yes | ~$42 | Kidney + liver function |
Affiliate disclosure: This article contains affiliate links. We may earn a commission if you purchase through them, at no extra cost to you.
Order BMP at HealthLabs — $34 → Order BMP at HealthLabs — $34 →Bottom Line
A ratio above 40:1 warrants prompt medical attention. For routine monitoring, order a BMP through HealthLabs for $34 — same CLIA-certified labs your doctor uses, results in 24-72 hours.
How We Reviewed This
BUN/creatinine ratio reference ranges in this article are sourced from Mayo Clinic Laboratory Reference Values and verified against LabCorp and Quest Diagnostics published reference ranges as of May 2026.