The term green onion is usually used interchangeably with spring onion and scallion. All are onions that don’t have a large bulb, either because they don’t grow that way or because they are harvested before the bulb forms. Green onions deliver a lot of the flavor of mature bulb onions, with a little less of the bite. And the green leaves are edible, which offers some different nutrients from bulb onions.
Green Onion Nutrition Facts
The following nutrition information is provided by the USDA for 1 medium (15g) raw green onion.1

Calories: 4.8
Fat: 0g
Sodium: 2.4mg
Carbohydrates: 1.1g
Fiber: 0.4g
Sugar: 0.4g
Protein: 0.3g
One raw green onion contains just over 1 gram of carbohydrate, about half of which is from fiber and the other half from sugar.

As with most non-starchy vegetables, green onions are not measured by the glycemic index. Because they have so little carbohydrate, they can’t be tested for glycemic index and are assumed to have a low GI. The glycemic load, which takes into account the amount that may be eaten, is also assumed to be very low; consuming them does not raise blood sugar.

Like most vegetables, green onions have virtually no fat.
Green onions also contain very little protein.