A simple sugar that passes into the urine and blocks common infection-causing bacteria from sticking to the bladder wall. Popular for preventing repeat urinary infections without antibiotics, though the strongest study found no benefit and evidence quality is low. Safety is excellent, with mild digestive upset the main issue. Broader immune, tumor, and aging effects remain speculative. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Urine culture | No significant growth; identify organism | Confirms E. coli and detects resistant or non-responsive organisms |
| Urinalysis (leukocyte esterase, nitrites) | Negative | Screens for active infection and inflammation |
| Fasting blood glucose | 70–90 mg/dL | Reassurance D-mannose is not raising glucose in diabetes |
| HbA1c | Below 5.4% | Longer-term glucose control where diabetes is a concern |
| eGFR (with creatinine) | Above 90 mL/min/1.73m² | Baseline kidney function before long-term or high-dose use |
Cadence: Urine culture at each suspected episode; review infection frequency at 3 and 6 months; recheck glucose and kidney function every 6–12 months in those with diabetes or kidney concerns