Erythrocyte folate before and during treatment with lithium

We determined erythrocyte folate in normal subjects (blood donors) as well as in manic--depressive patients before the start of prophylactic lithium treatment and at various times during the treatment. Before treatment the patients' erythrocyte folate was 25 per cent lower and after 6 months of treatment it was 10 per cent lower than the control value. Thereafter patient values and control values did not differ. Lithium treatment accordingly normalised on abnormal folate balance, but it is also possible that lithium in itself may have elevated erythrocyte folate. This is supported by animal data. Rats were given ordinary food and food containing lithium. After eight weeks erythrocyte folate was 27 per cent higher in the lithium-treated rats than in the controls. Our study does not support the notion that folate supplements are required during lithium therapy.