What kind of interaction is it?

Caution: an interaction that may reduce efficacy or raise side-effect risk and warrants monitoring.

Is this interaction backed by published research?

Yes. NutriStack lists 1 citation row for the Ampicillin + Vitamin K1 pair, each linking to PubMed by PMID where available. Full sourcing methodology at https://nutristackapp.com/methodology/interactions.

Supplement × Prescription·a caution·Emerging evidence

Ampicillin + Vitamin K1

Q: Can I take Ampicillin and Vitamin K1 together?

Possibly, but with caution. Ampicillin and Vitamin K1 have a documented caution-tier interaction. Prolonged Ampicillin therapy can contribute to reduced vitamin K status in susceptible patients by altering gut flora, with higher concern in poor intake, malabsorption, liver disease, or warfarin use.

Q: How does this affect a NutriStack Stack Score?

-5 to your Stack Score per scored caution row.

Caution Emerging evidence

Prolonged Ampicillin therapy can contribute to reduced vitamin K status in susceptible patients by altering gut flora, with higher concern in poor intake, malabsorption, liver disease, or warfarin use.

Supplement × Prescription

Open the interaction checker → Read the methodology

From the database

What the row says.

Every entry follows the same shape: what is happening, the mechanism, and the recommendation.

Substances

Ampicillin and Vitamin K1

Pair type

Caution

Evidence

Emerging

Source citations

Scope

Supplement × Prescription

Last verified

June 4, 2026

CautionEmerging evidence

What is happening. Prolonged Ampicillin therapy can contribute to reduced vitamin K status in susceptible patients by altering gut flora, with higher concern in poor intake, malabsorption, liver disease, or warfarin use.

Mechanism. Suppression of intestinal bacteria can reduce menaquinone production and may contribute to hypoprothrombinemia in high-risk patients.

Recommendation. Do not self-treat bleeding or INR changes. Monitor for bruising or bleeding and coordinate vitamin K or anticoagulant changes with the prescriber.

Stack Score

How it moves the number.

Effect on the composite score

If both Ampicillin and Vitamin K1 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 at /methodology/stack-score.

Sources

Sources, by evidence tier.

Every claim on this page is cited. PMIDs link straight to PubMed.

Reference material

1Shearer MJ. Vitamin K deficiency bleeding and antibiotic-associated hypoprothrombinemia. Review.Needs sourceNo link

Check your full routine

One pair was the worked example.

Drop your supplements and prescriptions into NutriStack and it runs every pair at once: every interaction, synergy, timing rule, and contraindication, each linked to its primary source.

Open the interaction checker → Browse the research index