Is onion low FODMAP?
High
Only in small amounts. Onion is low FODMAP up to 10 g (1 small ring), less than a usual serving. At 12 g (1 small ring) it is moderate in fructans. This is for raw white onion; other forms are below.
How much stays low
Low up to 10 g
- Low up to
- 10 g
- Not low from
- 12 g (1 small ring)
- High from
- 75 g (¾ medium or ½ cup)
Each mark is a rated serving. Between two marks the higher rating applies; past the last one nothing is rated.
Every rated serving
| Amount | Rating | Not low in |
|---|---|---|
| 10 g (1 small ring) | Low | All six groups low |
| 12 g (1 small ring) | Moderate |  Fructans |
| 75 g (¾ medium or ½ cup) | High | Fructans GOS |
Low means every FODMAP group is under its per-serving cut-off. Moderate and high are the two steps above it. FODMAPs add up across a meal, so several low servings together can be too much.
Other forms
Ripeness, the part you eat and how it’s prepared can change the answer.
- Spanish or red onion, rawLow up to 10 g
Check your whole plate, not just one food
FODMAPs add up across a meal. Snap your plate in Fodmi to see the total, then check in later on how it sat.
Where the numbers come from
Fodmi estimates FODMAP content from published food composition data. It is not medical advice. Tolerance varies from person to person; follow a low FODMAP diet with a qualified health professional.
Data from Fodmi’s food catalog, checked October 28, 2026.Sources and method