The aim of this study is to find out the effect of phenylhydrazine on creatinine clearance, hence GFR and the relationship between GFR and aldosterone. Sixteen 16 male Wistar rats weighing 200 – 250 grams were randomly divided into four groups namely: Group 1 – Normal control Group 2 - Hematinic group (Fes): fed normal rat chow + tap water + ferrous sulphate (using an oral gavage at 75mg/kg bw); Group 3 - Anemic -treated group (AFes): administered Phenylhydrazine (PHZ) intraperitoneally for two consecutive days to induce anemia at a dose of 40mg/kg bw + normal rat chow + tap water + ferrous sulphate at 75mg/kg bw. Group 4 (Anu) – Anemic control group: administered Phenlyhydrazine (PHZ) intraperitoneally at a dose of 40mg/kg of bw + normal rat chow + tap water (as in group one). After 15 days, blood and urine samples were collected into sterile sample bottles for analysis. There was a significant (P<0.01, P<0.01, P<0.05) increase in aldosterone levels between Anu, control, Fes and AFes respectively. There was a significant (P<0.001) decrease in control compared with Anu. There was also a significant (P<0.01, P<0.001) decrease in Fes with AFes and Anu. Anu creatinine clearance was also significantly (P<0.001) lower than AFes. Phenylhydrazine intoxication led to a reduction in creatinine clearance and an increase in aldosterone levels, confirming a negative correlation (r= 0.9956, P<0.01) between aldosterone and creatinine clearance. Also, ferrous sulphate tends to reduce the extent to which aldosterone levels increased hence narrowing the margine and or reducing the significance of the correlation.