Cranberry
Cranberry products are dietary preparations sometimes used in an attempt to reduce the recurrence of urinary tract infections.
Adult dose
Dose adjustments
Not a dose adjustment: the SPC contraindicates use in current or previous kidney disease including kidney stones, in oedema secondary to heart failure or impaired renal function, in patients with kidney disorders who have experienced recurrent urinary tract infections, and in conditions where reduced fluid intake is recommended (e.g. severe cardiac or renal diseases) (§4.3, §4.4).
No hepatic dose adjustment or hepatic information is printed in the SPC.
Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.
Contraindications
- Hypersensitivity to cranberry (Vaccinium macrocarpon Ait.) fruit or to any of the excipients (§4.3)
- Oedema secondary to heart failure or impaired renal function (§4.3)
- Current or previous kidney disease including kidney stones (§4.3)
- Patients with kidney disorders who have experienced recurrent urinary tract infections (§4.3)
- Conditions where a reduced fluid intake is recommended, e.g. severe cardiac or renal diseases (§4.3)
- Concomitant use of warfarin and other anticoagulant medicines (§4.3, see §4.5)
- Concomitant use of tacrolimus and immunosuppressant drugs (§4.3, see §4.5)
- Concomitant use with chemotherapy (§4.3, see §4.5)
- Use in men is not recommended; use in pregnant women is not recommended (§4.2, §4.4)
- Not recommended in children and adolescents under 18 years old (§4.2, §4.4)
Side effects
- Gastrointestinal disorders: nausea or vomiting, diarrhoea, dyspepsia, constipation, abdominal pain or discomfort (§4.8)
- Skin and subcutaneous tissue disorders: urticaria and rash (hypersensitivity reaction) (§4.8)
- The frequency is unknown and cannot be estimated from the available data (§4.8)
Interactions
- Warfarin: individual case reports suggest a possible interaction with cranberry juice, in most cases leading to an increase in INR or bleeding event; other vitamin K antagonists such as acenocoumarol and phenindione could also potentially interact; the concomitant use of anticoagulant medicines and cranberry juice products is contraindicated (§4.5, §4.3)
- Direct-acting oral anticoagulants (apixaban, edoxaban, dabigatran, rivaroxaban) and parenteral anticoagulants (heparin, dalteparin, enoxaparin, tinzaparin): no reports of interaction to date, although a clinical study demonstrates a potential pharmacodynamic interaction between cranberry and warfarin (§4.5)
- Amoxicillin and cefaclor: no evidence that cranberry juice has a clinically relevant effect on their pharmacokinetics (§4.5)
- Tacrolimus: a case study reported that concurrent administration with cranberry juice resulted in a significant reduction in tacrolimus levels; patients taking immunosuppressant drugs should not take cranberry preparations (§4.5, §4.3)
- Chemotherapy: an in vitro study suggested that cranberry inhibits CYP2C8 (an enzyme pathway for metabolising many drugs, including paclitaxel); there are no human studies showing an interaction with paclitaxel, but patients receiving chemotherapy should not take cranberry products (§4.5, §4.3)
Monitoring
- Do not exceed the stated dose (§4.4)
- Seek medical advice or take usual treatment if the symptoms of a UTI appear, and seek medical advice if the patient is not sure if she has a UTI (§4.4)
- Consult a doctor immediately if any of the following develop: fever, rigors, abdominal pain, spasms, back pain, haematuria, dysuria, urinary retention or urinary incontinence (§4.4)
- If UTIs recur more often, a doctor should be consulted for advice on adjusting the frequency of treatment (§4.2)
- Cranberry contains oxalate; there may be an increased risk of stone formation in the urinary tract in patients with a stone history (§4.4)
Clinical monograph
How it works
Cranberry contains proanthocyanidins that are proposed to interfere with adhesion of certain bacteria, such as Escherichia coli, to the urinary tract epithelium.
Prescribing in practice
- Cranberry is not a treatment for an established urinary tract infection and should not replace antibiotics where these are indicated.
- It may potentiate the effect of warfarin, so caution and closer anticoagulation review are advised in patients taking warfarin.
- Evidence of benefit is limited and inconsistent, and it should not delay appropriate medical assessment of urinary symptoms.
Monitoring
No specific laboratory monitoring is required, but review anticoagulation control in patients taking warfarin.
Counselling the patient
- Cranberry does not treat an active infection; seek medical advice if you have urinary symptoms.
- Tell your clinician you are taking cranberry if you are on warfarin.
Evidence & guidelines
Evidence for cranberry in preventing recurrent urinary tract infection is limited and inconsistent across systematic reviews.
Reference: Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.