Severe infections can cause increased phosphate levels, resulting in hyperphosphatemia. Cell destruction - from chemotherapy, when the tumor cells die at a fast rate. This can cause tumor lysis syndrome. Problems with your breathing (respiratory acidosis)

Does chemo cause low phosphate?

Platinum chemotherapy, particularly cisplatin, is commonly associated with electrolyte imbalances, including hypomagnesemia, hypokalemia, hypophosphatemia, hypocalcemia and hyponatremia.

What are the causes of hyperphosphatemia?

Hyperphosphatemia is a serum phosphate concentration > 4.5 mg/dL (> 1.46 mmol/L). Causes include chronic kidney disease, hypoparathyroidism, and metabolic or respiratory acidosis. Clinical features may be due to accompanying hypocalcemia and include tetany. Diagnosis is by serum phosphate measurement.