Vitamin K1 · low result
What does a low Vitamin K1 mean?
Short answer
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.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
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.
Full reference table, citations and testing options: Vitamin K1 biomarker page.
What are the common causes of low Vitamin K1?
- Low intake of leafy green vegetables
- Fat malabsorption: celiac disease, Crohn's, cystic fibrosis, pancreatic insufficiency, cholestasis
- Prolonged broad-spectrum antibiotics
- Bariatric surgery, very low-fat diets
- 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 available at TestWell: PT and PTT (Prothrombin & Partial Thromboplastin Time) ($54.99).
How do you recheck Vitamin K1?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Vitamin K | Test | $36.99 | No | 5–7 business days |
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.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.