A concentrated fruit extract standardised to type-A proanthocyanidins, the compounds associated with reduced bacterial adhesion in the urinary tract. Juice, powder and standardised extract deliver very different amounts.
Cranberry is one of the few botanicals where a large body of randomised trials, summarised by an updated Cochrane review of around 50 studies, supports a specific narrow use: fewer recurrent urinary tract infections in women with repeated infections, in children, and after certain urological procedures. It has not been shown to help people with catheters, older adults in care homes, or people with neurogenic bladder, and it is not a therapy for an established infection.
Sold as
Standardised PAC extract capsule, Juice, Powder, Tablet, Dried fruit
Standardised to
Trials commonly specify 36 mg of type-A proanthocyanidins per day by a defined assay method — a product without this marker may not resemble what was studied.
The amounts, forms and durations published trials of Cranberry extract actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Recurrent urinary tract infection in women
36–72 mg
Moderate
Type-A proanthocyanidins from standardised extract, daily · 6–12 months
Trials specify proanthocyanidin content by assay, and different assay methods give different numbers for the same product, so label comparisons are unreliable. Juice trials used 240–300 mL daily, which is a large sugar load over months.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🌙Evening
Not enough
Some protocols dose in the evening on the reasoning that overnight urine dwell time is longest. This has not been compared against morning dosing in a trial.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
🔀Split through the day
Limited
Twice-daily dosing is common in trials to maintain urinary levels across the day, following pharmacokinetic reasoning rather than a head-to-head comparison.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Strong
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
A large updated systematic review of around 50 randomised trials found cranberry products reduced the rate of repeat urinary tract infections in women with recurrent infections, in children and after urological procedures. It did not help people with catheters or bladder-emptying disorders, and it is not a therapy for an active infection — which needs antibiotics and assessment.
What may be going on: Type-A proanthocyanidins reduce adhesion of P-fimbriated Escherichia coli to bladder epithelium in laboratory models.
Strong evidence. Consistent findings across multiple good-quality human studies.
Evidence is limited for cranberry extract and oxidative stress markers. Most of that work is in cell models or measures antioxidant assays rather than human outcomes.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Interaction
Warfarin
Interacts withWarfarin
Case reports and regulatory advisories describe raised INR and bleeding in people taking warfarin with cranberry products, though controlled studies have been inconsistent. UK guidance advises caution and closer monitoring.
Worth knowing
Not a therapy for an active infection
Cranberry reduces recurrence rates; it does not clear an established urinary infection. Fever, back pain or blood in urine needs prompt medical assessment rather than a supplement.
Worth knowing
Kidney stones and oxalate
Cranberry is relatively high in oxalate and has been associated with increased urinary oxalate excretion, which matters for anyone with calcium oxalate kidney stones.
Worth knowing
Sugar load in juices
Cranberry juice cocktails are heavily sweetened, and the volumes used in trials taken daily for months represent a substantial sugar intake.
Worth knowing
Proanthocyanidin content is inconsistently measured
Different laboratory methods report different proanthocyanidin values for the same product, so two capsules claiming 36 mg may not deliver the same thing.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.