The short answer
Tell your transplant team before using a cranberry extract. One report linked a concentrated cranberry product to a low tacrolimus level, but it does not prove that all cranberry products lower tacrolimus or establish a predictable effect.
What this answer covers
The report involved cranberry juice extract capsules, not a measured serving of juice or whole cranberries. The product's precise composition and botanical species were not verified, which limits its application to Vaccinium macrocarpon.
- Supplement or preparation
- Cranberry (Vaccinium macrocarpon)
- Medication ingredient
- tacrolimus
What happened in the reported case?
A kidney-transplant recipient taking cranberry extract 1,000 mg twice daily developed a very low tacrolimus trough despite dose increases. After the extract was stopped while the higher tacrolimus dose continued, the level rose. Her graft function stayed normal throughout the episode.
How certain was the explanation?
The authors rated the interaction as possible. This was one person, the product was not restarted to test the explanation, and the tacrolimus dose changed during the episode. The proposed mechanism remained speculative. These limitations make a predictable decrease uncertain.
Does this apply to juice or whole fruit?
The case cannot establish an effect from an ordinary glass of cranberry juice, whole cranberries or a different capsule. Extract strength and constituents were not established. It also does not prove those other exposures are safe, so discuss concentrated products and major changes in use with your team.
What should I do if I already use cranberry?
Give your transplant team the product label, amount and dates of use, including any recent start or stop. They can decide whether a trough level needs checking. Do not increase tacrolimus to compensate for cranberry or rely on a spacing interval; the case provides no validated dosing rule.
Evidence and practical considerations
Absorption & effectiveness
A single possible cranberry-extract interaction involved lower tacrolimus troughs; causality, mechanism and generalizability remain uncertain.
- Exact scope
- Cranberry juice extract capsules 1,000 mg twice daily; botanical species and composition incompletely verified. with Tacrolimus, exact RxCUI 42316, inventory name tacrolimus, TTY IN. Oral systemic tacrolimus only. The US PROGRAF label describes tacrolimus capsules and anhydrous-equivalent strength; the UK capsule SmPC section 2 explicitly states tacrolimus as monohydrate. This bridges labeled monohydrate capsules to the IN, without merging different release formulations or transferring exposure results to topical or intravenous tacrolimus. No cyclosporine or other immunosuppressant evidence is substituted for tacrolimus evidence.
- Medication form and route
- oral
What remains uncertain
- No rechallenge, changing doses, concurrent cephalexin initiation and no replication identified in targeted search.
Read the supporting source summaries
Source 1: original human case report
pmc.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: A 40-year-old woman four years after kidney transplantation, receiving tacrolimus, mycophenolate and prednisone.
Trough tacrolimus fell from about 8.1 to below 2 ng/mL despite dose increases; after extract withdrawal with the higher dose maintained, the level rose to 11 ng/mL. Kidney graft function stayed normal. DIPS score 4 indicated a possible interaction.
How this applies: A clinical caution about one concentrated cranberry product. A tentative common-name bridge to V. macrocarpon does not confirm every extract, juice or whole-fruit exposure.
One case, no rechallenge, changing tacrolimus doses, concurrent antibiotic initiation and uncertain product identity. The proposed enzyme-induction mechanism was speculative and opposite the inhibition expected from other cranberry experiments.
Research assessment: · Open full citations ↗
Timing & monitoring
Product review and individualized tacrolimus monitoring are prudent around concentrated cranberry use; no universal spacing or dose adjustment follows.
- Exact scope
- Concentrated cranberry products; ordinary juice and fruit not measured by this case. with Tacrolimus, exact RxCUI 42316, inventory name tacrolimus, TTY IN. Oral systemic tacrolimus only. The US PROGRAF label describes tacrolimus capsules and anhydrous-equivalent strength; the UK capsule SmPC section 2 explicitly states tacrolimus as monohydrate. This bridges labeled monohydrate capsules to the IN, without merging different release formulations or transferring exposure results to topical or intravenous tacrolimus. No cyclosporine or other immunosuppressant evidence is substituted for tacrolimus evidence.
- Medication form and route
- oral
What remains uncertain
- Precaution derived from a possible case and the medication monitoring label.
Read the supporting source summaries
Source 1: original human case report
pmc.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: A 40-year-old woman four years after kidney transplantation, receiving tacrolimus, mycophenolate and prednisone.
Trough tacrolimus fell from about 8.1 to below 2 ng/mL despite dose increases; after extract withdrawal with the higher dose maintained, the level rose to 11 ng/mL. Kidney graft function stayed normal. DIPS score 4 indicated a possible interaction.
How this applies: A clinical caution about one concentrated cranberry product. A tentative common-name bridge to V. macrocarpon does not confirm every extract, juice or whole-fruit exposure.
One case, no rechallenge, changing tacrolimus doses, concurrent antibiotic initiation and uncertain product identity. The proposed enzyme-induction mechanism was speculative and opposite the inhibition expected from other cranberry experiments.
Source 2: regulatory prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients receiving systemic tacrolimus for transplant immunosuppression; oral capsules and granules discussed separately from injection.
Requires drug-level monitoring and individualized dosing. Warns of nephrotoxicity, infections, neurotoxicity, QT prolongation and hyperkalemia. Avoid grapefruit and juice; CBD needs close monitoring and possible dose reduction.
How this applies: Medication-specific safety and monitoring context. Additional supplement-specific findings and explicit formulation boundaries are required.
Label warnings do not quantify the added clinical-event risk from each supplement. The oral products are not freely interchangeable; topical use is outside these data.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Original evidence and current product information inspected; article distinguishes observed results, product limits and remaining uncertainty. | |
| Research summary published |
Article revision: b0e7b374fd64828d
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.