Is onion high in oxalate?
A
No. Very low, 1.9 mg per 1 medium onion
Range 0 to 2.1 mg across 3 studies, 110 g serving
0 mg50 mg = a day60 mg+
Onion is low in oxalate: about 1.9 mg per 1 medium onion, which is 4% of the 50 mg a day many stone clinics aim for.
Where this number comes from
Each row is one published measurement, converted to a 110 g serving (1 medium onion). 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 |
|---|---|---|---|
| 0 mg | 0 mg | Raw | Kim D.-J., Kim H., Kim M., Lee J, 2007via Foods 2023;12:3201, Table 5 (CC BY 4.0) |
| 0 mg soluble only* | 0 mg | Raw (n=6) | Santamaria P., Elia A., Serio F., Todaro E, 1999via Foods 2023;12:3201, Table 5 (CC BY 4.0) |
| 1.9 mg | 1.7 mg | Raw (n=2) | Hönow R., Hesse A, 2002via Foods 2023;12:3201, Table 5 (CC BY 4.0) |
| 2.1 mg | 1.91 mg | Raw | Harvard T.H, 2023 |
* 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