Cranberry safety: kidney stones and warfarin interactions
What it found
In people and animals, cranberry was not linked to serious side effects, though warfarin interactions and kidney stones were flagged as possible risks.
The authors say cautionary labels are not needed for quality standards.
What they found
Studies in people
Warfarin and juice
Interactions with warfarin were not associated with moderate intakes of cranberry juice (240 to 480 mL).
High intakes and warfarin
Some reports suggested warfarin interactions may need excessive intakes of cranberry juice (1 to 2 L/day) or cranberry extracts (3000 mg/day).
Warfarin case details
Cases of warfarin interactions with cranberry have mostly involved patients with serious illnesses and/or individuals taking other medications at the same time.
Studies in people and animals
Serious side effects
Published clinical and animal data indicated that cranberry is not associated with serious adverse effects.
Kidney stone risk
Studies gave contradictory results on whether cranberry plays a role in kidney stone formation. Some reports suggested cranberry is linked to a reduced risk of kidney stones.
What the authors conclude
“Based on the totality of the data, the U. S. Pharmacopeial Convention concluded that cranberry ingredients are not known to be associated with serious risks to human health when consumed properly in dietary supplements and therefore were admitted for standard development.”
Also in their conclusions
- They concluded that cranberry ingredients are not known to be associated with serious risks to human health when consumed properly in dietary supplements.
- They concluded that cautionary labeling statements about warfarin interactions or kidney stone formation are not necessary for quality standards.
How it was done
Cranberry is a popular dietary supplement ingredient, and the U.S. Pharmacopeial Convention wanted to know if any safety issues should stop it from setting quality standards for cranberry ingredients.
They reviewed published clinical and animal data on cranberry, looking at side effects, kidney stone formation, and interactions with the blood thinner warfarin.
What it can’t tell you
- We summarised it from the abstract only.
- This review looked at published reports, so it cannot prove that cranberry causes or prevents kidney stones or warfarin interactions.
- The warfarin cases mostly involved people who were already seriously ill or taking other medications, so the role of cranberry alone is unclear.
Who paid
- Conflicts
- The authors declare that they have no conflict of interest.
- Authors work at
- Auburn University, AL
The paper
- Title
- Safety of Cranberry: Evaluation of Evidence of Kidney Stone Formation and Botanical Drug-Interactions
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Abstract only
- Cite
- Madden E, McLachlan C, Oketch-Rabah H, Calderón AI (2021). Safety of Cranberry: Evaluation of Evidence of Kidney Stone Formation and Botanical Drug-Interactions. Planta medica. doi:10.1055/a-1497-6241PubMed 34015833DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error