---
title: "What does a low BUN mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/bun/low"
biomarker: BUN
direction: low
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 low BUN mean?

> A low BUN is usually unremarkable — a low-protein or vegetarian diet, overhydration, pregnancy, or a small body — but it can accompany liver disease, because the liver makes urea, and severe malnutrition. On its own it rarely needs follow-up.


## What is the normal range for BUN?

- age 18+: 7.00 – 20.0 mg/dL

Can reflect low-protein intake, liver disease, or overhydration.

## What are the common causes of low BUN?

1. Low-protein diet, malnutrition
2. Overhydration
3. Pregnancy
4. Liver disease (reduced urea production)

## What symptoms go with low BUN?

- None from the BUN itself

## What do clinicians usually check next?

- Liver panel if unexplained
- Nutrition review

## 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

### Should I worry about a low BUN?

Usually not. It reflects diet or hydration far more often than disease.

## Related

- [What does a high BUN mean?](https://www.test-well.com/biomarkers/bun/high)
- [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/low
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.