The therapeutic efficacy of a crude water extract of Khaya grandifoliola has been established in mice. This study was designed to assess the effect of the extract on the red blood cells and bone for 7 days, 3 weeks and a recovery period of 3 weeks. Daily administration of the extract showed no related adverse effects on the mortality rate, physical appearance or behaviour of the rats. A general pattern of significant (p < 0.5) increases in the red blood cell (RBC) count, PCV, haemoglobin and plasma iron content was shown by groups administered with extract after 7 and 21 days when compared with control rats. There was a general trend of reduction in the bone minerals determined (Ca, P, Mg and Cu) in the extract administered groups. Significant (p < 0.5) decreases were observed at the 500 mg/kg concentration. The bone potassium and iron content was significantly (p < 0.5) increased in rats administered with extract in a dose-dependent manner. There was an observed significant (p < 0.5) decrease in alkaline phosphatase (ALP) activity in the rats administered with the extract when compared with the control animals. During the recovery period, the haematological indices regressed to values which were still significantly (p < 0.5) higher than those of the control values. These results indicate that K. grandifoliola has a positive effect on erythropoeisis, but no significant effect on bone mineral contents at therapeutic doses. At extremely high doses and during prolonged administration, it may have an adverse effect on bone minerals.