Severe lithium poisoning requires intensive and prolonged hemodialysis (HD) treatment in addition to supportive therapy. Aggressive dialytic therapy can bring about hypophosphatemia, especially, in those patients who are normo- or hypophosphatemic to begin with. We report here the use of phosphorus (P)-enriched HD in a hypophosphatemic patient with lithium poisoning. A 58-year-old woman with a long history of bipolar disorder treated with chronic lithium therapy presented with progressively worsening confusion and incoherent speech. She was noted to be confused with a labile mood. The serum levels were lithium 3.6 mM, creatinine 1.7 mg/dL, Na 136 mM, K 4.2 mM, CO2 21 mM, BUN 23 mg/dL, and P 2.1 mg/dL. After a conventional, 4-h HD session, she became more hypophosphatemic with a P level of 1.8 mg/dL. A P-enriched dialysate, prepared by adding a Fleet® oral saline laxative preparation (containing NaH2PO4.H2O and Na2HPO4.7H2O) to the “base concentrate” of a dual concentrate, bicarbonate-based dialysate generating system to obtain a final dialysate containing 3 mg (0.97 mM) of P/dL was used. She underwent 3 subsequent HD sessions using this P-enriched dialysate, followed by normalization of the serum levels of both lithium and P. Our data suggest that hypophosphatemic patients suffering from severe lithium poisoning requiring intensive HD therapy and becoming more hypophosphatemic as a result of the dialysis treatment can be further dialyzed with a P-enriched dialysate both to treat the lithium poisoning and to rectify the hypophosphatemia. In general, the use of such dialysates can play an important role in the prevention and treatment of dialysis-induced hypophosphatemia.