---
title: "What does a low Vitamin B2 (Riboflavin) mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/vitamin-b2-riboflavin/low"
biomarker: Vitamin B2 (Riboflavin)
direction: low
reference_range:
  - "age 18+: 137 – 370 nmol/L"
reviewed_at: 2026-09-08
review_status: reviewed
date_published: 2026-09-05
---

# What does a low Vitamin B2 (Riboflavin) mean?

> Low riboflavin (vitamin B2) is uncommon in the US and points to a diet low in dairy, eggs, meat and fortified grains — strict vegan or very restricted eating — or to alcohol use, malabsorption, hypothyroidism, or medications that interfere with it (some antidepressants, phenothiazines, long-term barbiturates). It rarely occurs alone; other B vitamins are usually low too.


## What is the normal range for Vitamin B2 (Riboflavin)?

- age 18+: 137 – 370 nmol/L

Can reflect inadequate dietary intake or malabsorption.

## What are the common causes of low Vitamin B2 (Riboflavin)?

1. Low intake: vegan or restricted diets without fortified foods
2. Alcohol use disorder, malabsorption, eating disorders
3. Hypothyroidism, adrenal insufficiency
4. Medications: tricyclics, phenothiazines, phenobarbital, probenecid
5. Phototherapy in newborns

## What symptoms go with low Vitamin B2 (Riboflavin)?

- Cracks at the corners of the mouth, sore red tongue, sore throat
- Scaly rash around the nose and mouth, eye irritation and light sensitivity
- Anemia, fatigue

## What do clinicians usually check next?

- B1, B6, B12 and folate — deficiencies cluster
- TSH, dietary review
- Riboflavin is inexpensive and safe to replete under clinician guidance; retest in 8–12 weeks

Follow-up tests at TestWell: [TSH (Thyroid Stimulating Hormone)](https://www.test-well.com/tests/tsh) ($26.99), [TSH + Free T4](https://www.test-well.com/tests/tsh-with-free-t4) ($27.99), [Folate (Vitamin B9)](https://www.test-well.com/tests/folate) ($32.99).

## How do you recheck Vitamin B2 (Riboflavin)?

| Test or panel | Type | Price | Fasting | Results |
| --- | --- | --- | --- | --- |
| [Vitamin B2 (Riboflavin)](https://www.test-well.com/tests/vitamin-b2-riboflavin) | Test | $66.99 | No | 3–5 business days |

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

## Common questions

### Can riboflavin help migraines?

High-dose riboflavin (400 mg/day) has evidence for migraine prevention in some trials; it is a separate use from correcting a deficiency and is a conversation for a clinician.

## Related

- [Vitamin B2 (Riboflavin) reference ranges](https://www.test-well.com/biomarkers/vitamin-b2-riboflavin)
- [Vitamin D, 25-Hydroxy reference range](https://www.test-well.com/biomarkers/vitamin-d-25-hydroxy)
- [Vitamin B12 reference range](https://www.test-well.com/biomarkers/vitamin-b12)
- [Folate reference range](https://www.test-well.com/biomarkers/folate)

## Sources

- [Quest Diagnostics](https://testdirectory.questdiagnostics.com/test/test-detail/14586/vitamin-b2)
- [MedlinePlus (NIH) — Vitamin B Test](https://medlineplus.gov/lab-tests/vitamin-b-test/)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-08. Review policy: https://www.test-well.com/editorial-policy

Canonical page: https://www.test-well.com/biomarkers/vitamin-b2-riboflavin/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.