Cranberry's compounds stop infection-causing bacteria from gripping the bladder wall. The strongest evidence supports standardized cranberry to prevent repeat urinary infections in women who get them often and in people vulnerable after catheters or surgery. It offers little for the frail elderly or in pregnancy and does not treat an active infection. Benefit depends on a properly dosed, standardized form. (Full Review)

Protocol

Standard Dose

~36 mg PAC/day

≈500 mg standardized extract once or twice daily, or 240–300 mL unsweetened juice

Dosing Pattern

Split dosing, with meals

Morning and evening preferred over a single dose; evening dose covers overnight

Form

Standardized PAC extract

Standardized extract or unsweetened juice, not sweetened juice cocktail

Time to effect

UTI Prevention

Weeks to months

Fewer infections over months of consistent use; reassess at ~3 months

Benefits

High: Prevention of recurrent urinary tract infections

Medium: Reduced reliance on antibiotics for urinary infections

Low: Cardiometabolic risk markers; oral and periodontal health

Speculative: Gut and vaginal microbiome modulation; antioxidant capacity and healthy aging; anticancer activity

Contraindications

History of calcium-oxalate kidney stones (concentrated extracts)

Warfarin without INR monitoring (concentrated extracts)

Known cranberry allergy (concentrated extracts)

Active infection (do not delay antibiotics)

Key Interactions

Antiplatelet and blood-thinning agents (aspirin, clopidogrel)

CYP2C9 substrates (diclofenac, celecoxib, phenytoin, glipizide)

OTC NSAIDs (ibuprofen, naproxen)

High-dose vitamin C

Risk & Side Effects

High: Gastrointestinal upset

Medium: Kidney stone risk

Low: Anticoagulant interaction and bleeding; sugar load and dental erosion from juice

Speculative: Salicylate sensitivity; broader drug-metabolism effects

Monitoring

Marker	Target	Why
Urinalysis and urine culture	No significant growth (<10⁵ CFU/mL)	Confirms true infection vs. irritation
Serum creatinine and eGFR	eGFR >90 mL/min/1.73m²	Baseline kidney function before concentrated use
24-hour urinary oxalate	<40 mg/24 h	Flags stone-forming risk
INR (if on warfarin)	2.0–3.0	Detects excess blood-thinning
Fasting lipid panel (TC/HDL ratio)	TC/HDL <3.5	Tracks cardiometabolic benefit
Fasting glucose and HbA1c	Glucose 70–90 mg/dL; HbA1c <5.4%	Tracks glucose and insulin effects
Blood pressure	<120/80 mmHg	Tracks blood-pressure effect

Cadence: Reassess UTI frequency at ~3 months, then every 6–12 months; INR within 1–2 weeks of starting for warfarin users; repeat urinary oxalate only with long-term concentrated extract use in stone-formers

Qualitative Assessment

Frequency and severity of urinary symptoms (urgency, painful urination, cloudy urine)
Length of the infection-free interval between recurrences
Absence of new gastrointestinal discomfort or diarrhea at the chosen dose
Overall energy and sense of well-being during high-risk periods

Cranberry for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment