Excessive consumption of iced tea has been linked to renal failure caused by oxalate nephropathy in a case study appearing in the New England Journal of Medicine. In the article, a 56-year-old man presented to the hospital with weakness, fatigue, body aches, and an elevated serum creatinine level (400μmol per liter). His previous medical records noted rising creatinine levels (110μmol per liter to 220μmol per liter); he had no proteinuria, hematuria, personal history of kidney stones, family history of kidney disease, history of gastric bypass surgery, or malabsorptive symptoms. However, his urine sediment was remarkable for the presence of abundant calcium oxalate crystals. Dialysis was initiated due to worsening renal failure with uremic symptoms.

Because ultrasonography showed normal kidney size despite the rapidly progressive nature of the patient’s renal failure, a renal biopsy was performed. Oxalate crystals, interstitial inflammation with eosinophils, and interstitial edema consistent with a diagnosis of oxalate nephropathy were observed in the sample. The patient admitted to drinking sixteen 8oz glasses of iced tea daily, which the doctors believe contributed to oxalate nephropathy leading to renal failure. The patient was consuming more than 1500mg of oxalate daily from black tea, which is 3–10 times more than the daily average American intake. With this conclusion, the author advises that in cases of unexplained renal failure in which proteinuria is absent and abundant oxalate crystals are present in urine sediment, a thorough dietary history should be obtained that includes assessing consumption of oxalate-rich sources like tea.