Background: No well‐defined protocols currently exist regarding the optimal rate and duration of normal saline administration to prevent contrast‐induced acute kidney injury ( CI ‐ AKI ) in patients with renal insufficiency. Methods and Results: Hydration volume ratios (hydration volume/weight; HV /W) were calculated in 1406 patients with renal insufficiency (estimated glomerular filtration rate [ eGFR ], <90 mL/min per 1.73 m 2 ) undergoing percutaneous coronary intervention ( PCI ) with routine speed hydration (1 or 0.5 mL/kg per hour). We investigated the relationship between hydration volume, risk of CI ‐ AKI (increase in serum creatinine ≥0.5 mg/dL or 25% within 48–72 hours), and prognosis. Mean follow‐up duration was 2.85±0.88 years. Individuals with higher HV /W were more likely to develop CI ‐ AKI (quartiles: Q1, Q2, Q3, and Q4: 4.3%, 6.6%, 10.9%, and 15.0%, respectively; P <0.001). After adjusting 12 confounders, including age, sex, eGFR , anemia, emergent PCI , diabetes mellitus, chronic heart failure, diuretics, contrast volume, lesions, smoking status, and number of stents, multivariate analysis showed that a higher HV /W ratio was not associated with a decreased CI ‐ AKI risk (Q2 vs Q1: adjusted odds ratio [ OR ], 1.13; Q3 vs Q1: adjusted OR , 1.51; Q4 vs Q1: adjusted OR , 1.87; all P >0.05) and even increased CI ‐ AKI risk ( HV /W >25 mL/kg: adjusted OR , 2.11; 95% CI , 1.24–3.59; P =0.006). Additionally, higher HV /W was significantly associated with an increased risk of death (Q4 vs Q1: adjusted hazard ratio, 3.44; 95% CI , 1.20–9.88; P =0.022). Conclusions: Excessively high hydration volume at routine speed might be associated with increased risk of CI ‐ AKI and death post‐ PCI in patients with renal insufficiency.