What Is a Normal Glycemic Index and What Do the Numbers Mean?

October 19, 2025 •

5 min read

According to the official glycemic index scale, foods are ranked from 0 to 100 based on their effect on blood sugar levels, with pure glucose arbitrarily assigned the value of 100. This tool helps classify carbohydrate-containing foods and guide dietary choices for better metabolic health.

Quick Summary

The glycemic index is a tool that ranks carbohydrate-containing foods from 0 to 100 based on their effect on blood glucose. Foods are categorized as low (55 or less), medium (56-69), or high (70 or more) GI, with lower values indicating a slower, more gradual rise in blood sugar.

Key Points

No Single 'Normal' Number: A normal glycemic index isn't a single value but a healthy eating pattern that prioritizes foods in the low (≤55) and medium (56–69) GI ranges.
Factors Affect GI: A food's glycemic index is influenced by its fiber, fat, and protein content, as well as its ripeness, how it's processed, and how it's cooked.
Glycemic Load is Crucial: Glycemic load (GL) is a more practical metric than GI, as it considers both a food's GI score and the actual portion size consumed.
Processing Increases GI: Highly processed and refined foods generally have a higher GI because they are more easily digested and absorbed by the body.
Balance is Key: To manage glycemic response effectively, combine carbohydrates with sources of protein, fiber, and healthy fats, and control portion sizes.
Not All Carbs Are Equal: The GI scale dispels the misconception that all carbohydrates have the same effect on blood sugar by ranking them based on their speed of digestion.

Understanding the Glycemic Index

To understand what is considered a normal glycemic index, it's first important to grasp what the index itself is. The glycemic index (GI) is a tool used in nutrition to classify foods containing carbohydrates based on their impact on blood sugar (glucose) levels. The system assigns a numerical value from 0 to 100 to carbohydrate-rich foods. Foods that are rapidly broken down during digestion and cause a fast, significant rise in blood glucose are given a high GI score. Conversely, foods that are digested slowly, leading to a more gradual increase in blood sugar, are given a low GI score.

Pure glucose serves as the reference point for the GI scale and is assigned a value of 100. The concept was originally developed to help people with diabetes manage their blood sugar, but it has since been adopted more widely as a guide for healthy eating. It is crucial to remember that only foods with carbohydrates are assigned a GI; items like meat, oils, and fats, which do not contain carbohydrates, do not have a GI score.

Defining the GI Ranges: Low, Medium, and High

Rather than one specific number, a “normal” glycemic index is best understood as a healthy dietary pattern that favors foods within the low to medium GI range. The GI scale is universally recognized with three main categories based on the food's numerical score:

Low GI (55 or less): Foods in this category are digested and absorbed slowly, causing a gradual rise in blood sugar. Examples include most fruits and non-starchy vegetables, legumes, and whole grains like steel-cut oats.
Medium GI (56–69): These foods have a moderate effect on blood sugar levels. Examples include whole wheat bread, basmati rice, and sweet potatoes.
High GI (70 or more): Foods with a high GI cause a rapid spike in blood glucose. Examples include white bread, potatoes, and highly processed snack foods.

What Determines a Food's Glycemic Index?

Several factors influence a food's GI, which is why the same type of food can have different GI values depending on how it's prepared.

Fiber Content

Foods high in soluble fiber, such as oats and legumes, generally have a lower GI. The fiber slows down digestion and the absorption of carbohydrates. In contrast, refined grains, which have had their fiber removed, typically have a higher GI. This is why a piece of whole fruit has a lower GI than fruit juice, which lacks fiber.

Nutrient Composition

Combining carbohydrates with protein and fat can lower a meal's overall GI. Fat and protein both slow down stomach emptying and digestion, which moderates the rise in blood sugar. For example, eating bread with peanut butter or a baked potato with sour cream will result in a lower GI response than eating the carbohydrate food alone.

Processing and Cooking

The more processed a food is, the higher its GI tends to be, as processing breaks down the food's structure, making it easier to digest. For instance, instant oatmeal has a higher GI than steel-cut rolled oats. Similarly, cooking methods matter. Pasta cooked al dente has a lower GI than overcooked pasta.

Ripeness

For fruits and vegetables, ripeness plays a role. A ripe banana has a higher GI than an unripe one because its starches have converted to sugars.

Acidity

Adding acid to a meal, such as vinegar or lemon juice, can lower the meal's GI by slowing the rate at which the stomach empties.

Glycemic Index vs. Glycemic Load: A Broader View

The glycemic index has a significant limitation: it does not account for portion size. To address this, nutritionists developed the concept of Glycemic Load (GL). GL is considered a more practical and complete measure because it factors in both the GI and the amount of carbohydrates in a typical serving.

Calculation: GL = (GI x grams of carbohydrate) / 100.

For example, watermelon has a high GI of around 72, but a single serving contains relatively few carbohydrates, giving it a low GL. Conversely, a large bowl of pasta may have a medium GI, but its high carbohydrate content results in a high GL.

Practical Tips for Managing Your Glycemic Response

Rather than obsessing over individual GI numbers, focus on these practical strategies for a healthier glycemic response:

Prioritize whole, unprocessed foods: Opt for whole grains, nuts, legumes, and most fruits and vegetables.
Combine carbohydrates with protein and healthy fats: Balance a higher GI food with protein or healthy fats to moderate its impact on blood sugar. For example, add chicken to a side of white rice.
Be mindful of portion sizes: Even low GI foods can raise blood sugar if eaten in very large quantities. Controlling portion size is key, as emphasized by the Glycemic Load concept.
Choose high-fiber options: Higher fiber content slows down digestion and helps stabilize blood sugar.

GI and GL Comparison for Common Foods


Food Item	Glycemic Index (GI)	Glycemic Load (GL) per serving	Notes
White Bread	75	10	High GI, but GL can be moderate depending on portion size.
Sweet Potato	54	10	Low GI and low GL, though cooking method can influence GI.
Watermelon	72	8	High GI, but low GL due to low carb density per serving.
Pasta (White, Al Dente)	46	20 (standard 180g serve)	Low GI, but a typical large portion results in a high GL.
Steel-cut Oats	55	11	Low GI and moderate GL, a healthier choice than instant oatmeal (high GI).
White Rice	87	20+	High GI and typically high GL, causing a rapid blood sugar spike.

Conclusion: Embracing a Balanced Approach

There is no single numerical answer to what is a normal glycemic index. Instead, a healthy dietary pattern prioritizes an abundance of low and medium GI foods while incorporating higher GI foods in moderation. The GI is a useful tool, particularly for people managing conditions like diabetes, but it should be viewed in the context of the overall diet. Considering the glycemic load, which accounts for portion size, provides a more accurate picture of a food's effect on blood sugar. Ultimately, focusing on a balanced diet rich in a variety of whole, unprocessed foods, combined with healthy cooking methods and controlled portion sizes, is the most effective strategy for managing blood sugar and supporting overall health. For more detailed information on specific foods, the University of Sydney maintains an extensive online database.

Frequently Asked Questions

There is no single 'good' number, but foods with a glycemic index (GI) of 55 or less are considered low and are beneficial for more stable blood sugar levels. A healthy diet focuses on a pattern of choosing low and medium GI foods more often.

Yes, cooking can affect a food's GI. For example, cooking pasta al dente results in a lower GI than cooking it for a longer period. Similarly, overcooked starches tend to have a higher GI.

Not necessarily. While low GI foods tend to be healthier, this is not always the case. Some processed foods that are high in fat and calories (like chocolate) may have a low GI due to the fat content slowing digestion. It is important to consider the overall nutritional value.

GL is often considered a more accurate and practical measure because it accounts for both the GI of the food and the quantity of carbohydrates in a typical serving. This provides a better real-world picture of a meal's total impact on blood sugar.

You can lower a meal's glycemic index by combining high GI carbohydrates with low GI foods. Adding protein, fat, and fiber to your meal will slow down digestion and moderate the blood sugar response.

No, this is a common misconception. The glycemic index was developed specifically to address the fact that different carbohydrates are digested at different rates, causing varying effects on blood glucose levels.

While the glycemic index was initially developed for diabetes management, it can be a useful tool for anyone seeking to make healthier dietary choices, manage weight, and improve overall metabolic health.