NutriStack
Ceftriaxone and Vitamin K2, a caution.
Ceftriaxone suppresses vitamin K-producing gut bacteria and has been associated with hypoprothrombinemia and bleeding, particularly in malnourished patients, the elderly, or those with prolonged therapy. Although ceftriaxone lacks the N-methylthiotetrazole side chain seen in some bleeding-prone cephalosporins, gut flora suppression alone can lower vitamin K2 stores.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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From the interaction database
What the row says.
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At a glance
- Substances
- Ceftriaxone and Vitamin K2
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Ceftriaxone suppresses vitamin K-producing gut bacteria and has been associated with hypoprothrombinemia and bleeding, particularly in malnourished patients, the elderly, or those with prolonged therapy. Although ceftriaxone lacks the N-methylthiotetrazole side chain seen in some bleeding-prone cephalosporins, gut flora suppression alone can lower vitamin K2 stores.
Mechanism. Ceftriaxone disrupts the colonic anaerobic flora responsible for synthesizing vitamin K2 (menaquinones), gradually depleting hepatic menaquinone stores and reducing gamma-carboxylation of clotting factors II, VII, IX, and X.
Recommendation. For short courses in well-nourished adults, no special action is needed. For prolonged therapy, malnutrition, elderly patients, or critical illness, monitor coagulation and discuss vitamin K2 supplementation with your clinician.
Sources (2)
- Shirakawa H, Komai M, Kimura S. Antibiotic-induced vitamin K deficiency and the role of the presence of intestinal flora. Int J Vitam Nutr Res. 1990;60(3):245-51. PMID 2276882
- Conly J, Stein K. Reduction of vitamin K2 concentrations in human liver associated with the use of broad spectrum antimicrobials. Clin Invest Med. 1994;17(6):531-539. PMID 7895417
Stack Score
How this pair moves the number.
Effect on the composite score
If both Ceftriaxone and Vitamin K2 are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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