Nutrient depletion·Vitamin K·Reviewed June 9, 2026
What depletes vitamin k?
20 medications in the NutriStack database are documented to lower Vitamin K with ongoing use, most notably Cholestyramine. The pattern spans 18 drug classes. Depletion builds slowly and is easy to miss; the table below shows how each medication drives it and which biomarker to check. Never start a replacement supplement without your prescriber's input.
Vitamin K depletion at a glance.
A quick, data-grounded summary. The per-medication table is below.
20 medications in the NutriStack database are documented to lower Vitamin K with ongoing use, most notably Cholestyramine. The pattern spans 18 drug classes. Depletion builds slowly and is easy to miss; the table below shows how each medication drives it and which biomarker to check. Never start a replacement supplement without your prescriber's input.
What is documented to lower vitamin k.
Worst documented severity first. Open any medication for its full interaction and depletion guide. Absence from this table means no documented record, not proven safety.
| Medication | Severity | How it lowers vitamin k | Monitor |
|---|---|---|---|
| Cholestyramine Bile acid sequestrant | Significant | Bile acid sequestration can impair vitamin K absorption and lower vitamin K dependent clotting factor activity. | Prothrombin time/INR |
| Carbamazepine Antiepileptic | Moderate | Long-term anticonvulsant enzyme induction may impair vitamin K-dependent pathways in susceptible users. | Undercarboxylated osteocalcin or clinical assessment |
| Phenytoin Antiepileptic | Moderate | Enzyme induction may lower vitamin K-dependent clotting factor support and vitamin K status in susceptible long-term users. | Undercarboxylated osteocalcin or clinical assessment |
| Amoxicillin Penicillin Antibiotic | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Amoxicillin-Clavulanate Penicillin/Beta-Lactamase Inhibitor Combination | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Ampicillin Aminopenicillin antibiotic | Mild | Broad-spectrum aminopenicillins suppress the colonic bacteria (notably Bacteroides and other anaerobes) that synthesize menaquinones (vitamin K2).... | Prothrombin time / INR (most useful in patients on warfarin or with poor nutritional status) |
| Azithromycin Macrolide Antibiotic | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Cefdinir Cephalosporin antibiotic | Mild | Like other broad-spectrum cephalosporins, cefdinir suppresses gut bacteria that synthesize menaquinone (vitamin K2). Reduced bacterial vitamin K... | Prothrombin time / INR (especially in patients on warfarin or with poor intake) |
| Cefixime Third-generation cephalosporin antibiotic | Mild | Broad-spectrum cephalosporins suppress colonic bacteria (notably Bacteroides species) that synthesize menaquinones (vitamin K2), reducing the... | Prothrombin time / INR (particularly in patients on warfarin or with marginal vitamin K status) |
| Cefpodoxime Cephalosporin antibiotic (third-generation) | Mild | As a broad-spectrum oral antibiotic, cefpodoxime suppresses the colonic bacteria that synthesize menaquinones (vitamin K2), which can reduce the... | Prothrombin time / INR (particularly in patients on warfarin or with bleeding risk) |
| Ceftriaxone Third-Generation Cephalosporin | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Cefuroxime Second-generation cephalosporin antibiotic | Mild | Broad-spectrum antibiotic suppression of vitamin K-producing colonic bacteria reduces the supply of menaquinones (vitamin K2). Unlike cephalosporins... | Prothrombin time / INR (consider in malnourished or anticoagulated patients on prolonged therapy) |
| Cephalexin First-Generation Cephalosporin | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Clarithromycin Macrolide Antibiotic | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Clindamycin Lincosamide Antibiotic | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Dicloxacillin Antistaphylococcal penicillin (penicillinase-resistant penicillin) | Mild | Like other broad-acting oral antibiotics, dicloxacillin can suppress vitamin K-producing (menaquinone-synthesizing) gut bacteria in the colon. In... | Prothrombin time / INR (especially in patients taking warfarin) |
| Erythromycin Macrolide antibiotic | Mild | Like most broad-spectrum oral antibiotics, erythromycin can suppress vitamin K-producing colonic bacteria. In patients with already marginal vitamin... | Prothrombin time / INR (especially in patients on warfarin) |
| Metronidazole Nitroimidazole Antibiotic/Antiprotozoal | Mild | Broad-spectrum antibiotic exposure can suppress gut bacteria that synthesize menaquinones, lowering vitamin K availability in susceptible patients. | PT/INR |
| Rifampin Rifamycin Antibiotic | Mild | By inducing hepatic cytochrome P450 enzymes, rifampin accelerates the metabolism and clearance of vitamin K, which can reduce vitamin K-dependent... | Prothrombin time / INR |
| Vancomycin Glycopeptide antibiotic | Mild | Oral vancomycin used to treat Clostridioides difficile infection suppresses the colonic bacteria that synthesize menaquinone (vitamin K2), which can... | Prothrombin time / INR (particularly in patients on warfarin or with low dietary vitamin K intake) |
If you need to restore vitamin k.
Repletion is not automatic: dose, form, and timing depend on the medication involved, and some pairings need separation from the very drug causing the depletion. Confirm with your prescriber before adding vitamin k.
Common vitamin k depletion questions.
Quick answers drawn from the table above.
Which medications deplete vitamin k?
20 medications in the NutriStack database are documented to lower vitamin k, including Cholestyramine, Carbamazepine, Phenytoin, Amoxicillin, and Amoxicillin-Clavulanate. Severity differs by drug; the full table with mechanisms and monitoring biomarkers is on this page.
How do I know if my vitamin k is low?
The biomarkers used to track vitamin k status in this context include Prothrombin time/INR, Undercarboxylated osteocalcin or clinical assessment, and PT/INR. If you take one of the medications above long term, ask your prescriber whether checking is worthwhile; depletion develops gradually.
Should I take a vitamin k supplement with these medications?
Not automatically. Documented depletion makes repletion worth discussing, but the right answer depends on your labs, dose, and the specific drug. Bring it up with your prescriber or pharmacist.
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