---
title: "What does a high BUN mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/bun/high"
biomarker: BUN
direction: high
reference_range:
  - "age 18+: 7.00 – 20.0 mg/dL"
reviewed_at: 2026-09-06
review_status: reviewed
date_published: 2026-09-05
---

# What does a high BUN mean?

> BUN (blood urea nitrogen) rises with dehydration, a high-protein diet, gastrointestinal bleeding, heart failure, steroids and reduced kidney function. It's read with creatinine: a BUN-to-creatinine ratio above about 20 suggests dehydration or bleeding rather than kidney disease, while both rising together points to the kidneys.


## What is the normal range for BUN?

- age 18+: 7.00 – 20.0 mg/dL

Often reflects dehydration, high-protein diets, or reduced kidney function.

## What are the common causes of high BUN?

1. Dehydration
2. High-protein diet or protein supplements
3. Reduced kidney function
4. Gastrointestinal bleeding, heart failure, shock
5. Glucocorticoids, tetracyclines, catabolic states

## What symptoms go with high BUN?

- Usually none
- Thirst, dark urine if dehydrated

## What do clinicians usually check next?

- Interpret with creatinine and eGFR
- Repeat hydrated
- Stool blood test if bleeding is possible

## How do you recheck BUN?

| Test or panel | Type | Price | Fasting | Results |
| --- | --- | --- | --- | --- |
| [Basic Metabolic Panel](https://www.test-well.com/tests/basic-metabolic-panel) | Test | $20.99 | Yes | 1–3 business days |

Plus one $6 lab processing fee per order; physician authorization included.

## Common questions

### Is high BUN a kidney problem?

Only when creatinine and eGFR agree. On its own, high BUN is more often dehydration or diet.

## Related

- [What does a low BUN mean?](https://www.test-well.com/biomarkers/bun/low)
- [BUN reference ranges](https://www.test-well.com/biomarkers/bun)
- [Glucose reference range](https://www.test-well.com/biomarkers/glucose)
- [Creatinine reference range](https://www.test-well.com/biomarkers/creatinine)
- [eGFR reference range](https://www.test-well.com/biomarkers/egfr)

## Sources

- [Mayo Clinic](https://www.mayoclinic.org/tests-procedures/blood-urea-nitrogen/about/pac-20384821)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-06. Review policy: https://www.test-well.com/editorial-policy

Canonical page: https://www.test-well.com/biomarkers/bun/high
Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt

Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.