---
title: "What does a low Vitamin K1 mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/vitamin-k1/low"
biomarker: Vitamin K1
direction: low
reference_range:
  - "age 18+: 0.100 – 2.20 ng/mL"
reviewed_at: 2026-09-08
review_status: reviewed
date_published: 2026-09-05
---

# What does a low Vitamin K1 mean?

> Low vitamin K1 (phylloquinone) reflects low intake of leafy greens or fat malabsorption — celiac or Crohn's disease, cystic fibrosis, cholestatic liver disease, bariatric surgery — and prolonged antibiotic courses that wipe out gut bacteria. Warfarin does not lower the level but blocks its use. The functional consequence is a prolonged PT/INR and bleeding tendency; the blood level itself swings with the last day's meals.


## What is the normal range for Vitamin K1?

- age 18+: 0.100 – 2.20 ng/mL

Can reflect fat-malabsorption disorders, antibiotic use, or anticoagulant therapy.

## What are the common causes of low Vitamin K1?

1. Low intake of leafy green vegetables
2. Fat malabsorption: celiac disease, Crohn's, cystic fibrosis, pancreatic insufficiency, cholestasis
3. Prolonged broad-spectrum antibiotics
4. Bariatric surgery, very low-fat diets
5. Newborns (routine vitamin K at birth prevents this)

## What symptoms go with low Vitamin K1?

- Easy bruising, nosebleeds, bleeding gums, heavy periods
- Often none

## What do clinicians usually check next?

- PT/INR — the test that shows whether the deficiency matters
- Fat-soluble vitamins A, D and E; celiac antibodies, stool fat if malabsorption is suspected
- Dietary correction; supplementation under clinician guidance (and never without the prescriber's input if you take warfarin)

Follow-up tests at TestWell: [PT and PTT (Prothrombin & Partial Thromboplastin Time)](https://www.test-well.com/tests/pt-and-ptt) ($54.99).

## How do you recheck Vitamin K1?

| Test or panel | Type | Price | Fasting | Results |
| --- | --- | --- | --- | --- |
| [Vitamin K](https://www.test-well.com/tests/vitamin-k-test) | Test | $36.99 | No | 5–7 business days |

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

## Common questions

### Does a low vitamin K level mean I'll bleed?

Only if the PT/INR is prolonged. The blood level is a snapshot of recent intake; clotting tests show whether the body has enough to work with.

## Related

- [Vitamin K1 reference ranges](https://www.test-well.com/biomarkers/vitamin-k1)
- [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

- [Mayo Clinic Labs](https://www.mayocliniclabs.com/test-catalog/overview/42365)
- [Testing.com (AACC) — Vitamin K1 Test: Check Your Levels, Get Results](https://www.testing.com/tests/vitamin-k/)

---

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-k1/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.