Is black tea high in oxalate?
Moderately. Moderate, 11 mg per 1 cup brewed
Range 6.5 to 15 mg across 2 studies, 240 g serving
Lower-oxalate swap: Coffee, grade A, about 1.5 mg per 1 cup brewed.
Black tea has a moderate amount of oxalate: about 11 mg per 1 cup brewed, which is 22% of the 50 mg a day many stone clinics aim for, or 11% of the 100 mg others allow.
50 or 100 mg a day: which target is yours
Why sources disagree on black tea
Brewing moves tea's number. In one 2002 study, loose leaf brewed for 5 minutes gave more than a tea bag brewed the same way. Three of the five rows here measured soluble oxalate only, which is why they show but don't grade.
Where this number comes from
Each row is one published measurement, converted to a 240 g serving (1 cup brewed). The grade and the range use the rows prepared the way the serving is eaten, and take the middle. How the grades work.
| Per serving | Per 100 g | Preparation | Source |
|---|---|---|---|
| 4.8 mg soluble only* | 2 mg | tea bag, 1-5 min brew (n=10) | Mahdavi R, Lotfi Yagin N, Liebman M, Nikniaz Z, 2013 |
| 6.5 mg | 2.7 mg | brewed | Harvard T.H, 2023 |
| 9.4 mg soluble only* | 3.9 mg | tea bag, 245 mL water at 90 C, 5 min (n=18) | Charrier MJ, Savage GP, Vanhanen L, 2002 |
| 12 mg soluble only* | 5 mg | loose leaf, 2.4 g in 245 mL, 5 min (n=9) | Charrier MJ, Savage GP, Vanhanen L, 2002 |
| 15 mg | 6.3 mg | brewed | Siener R, 2021 |
* The study measured soluble oxalate only, which understates the total, so it's shown but doesn't set the grade.
By Oliver Silen · Data checked November 2, 2026 · Not medical advice