Vitamin C and Warfarin: interaction, severity and spacing
Vitamin C and Warfarin interact because very high vitamin C doses can reduce warfarin’s effect and have been reported to interfere with INR stability. Take them with care. Mild risk.
The interaction in detail
| Pair | Vitamin C and Warfarin |
|---|---|
| Type | Nutrient–drug interaction |
| Severity | Mild |
| Required spacing | None specified |
| Onset | At the time of dosing |
Mechanism
Very high vitamin C doses can reduce warfarin’s effect and have been reported to interfere with INR stability.
What to do
Keep vitamin C under 1000 mg per day while on warfarin and keep the dose consistent.
How to fit both into one day
Vitamin C is best split across the day in 250-500 mg doses because absorption saturates. Take a dose with iron to multiply uptake.
An evening dose is conventional so the INR drawn the next morning reflects a stable interval. Keep vitamin K intake consistent.
Putting Vitamin C in the morning and Warfarin in the evening satisfies the 0-hour separation without disrupting either one's absorption window.