What is the GI of Milk and How Does it Affect Your Health?

December 3, 2025 •

3 min read

Milk is generally considered a low-glycemic index (GI) food, with studies showing its GI value often falls between 30 and 39. This places it well within the low category, meaning it has a minimal impact on raising blood sugar levels compared to high-GI foods. The relatively low GI of milk is influenced by its composition, which includes proteins, fats, and a naturally occurring sugar called lactose.

Quick Summary

Milk is a low-glycemic food, primarily due to its protein, fat, and lactose content, which collectively slow carbohydrate absorption. This makes it a suitable option for blood sugar management, though factors like fat content, processing, and added sugars can alter its glycemic response. Plant-based alternatives also exhibit varying GI values.

Key Points

Low Glycemic Index: The GI of milk typically falls in the low range of 30-39, meaning it causes a slow and gradual rise in blood sugar.
Lactose's Role: The natural sugar in milk, lactose, is digested more slowly than other sugars, which helps to minimize the glycemic response.
Protein and Fat Effects: Both the protein and fat content in milk contribute to its low GI by slowing down carbohydrate digestion and absorption.
Added Sugars Increase GI: Flavored and sweetened milk products will have a higher GI and should be limited, especially for individuals monitoring their blood sugar.
Plant-Based Milk Variation: The GI of plant-based milk alternatives like rice milk and oat milk can be higher, while unsweetened soy or almond milk can have a low GI similar to cow's milk.
Glycemic Load Matters: It's important to consider both the GI and the portion size, known as Glycemic Load (GL), to understand a food's full impact on blood sugar.

Understanding the Glycemic Index

To understand why milk has a low glycemic index, it's essential to grasp what the GI represents. The Glycemic Index (GI) is a numerical scale from 0 to 100 that ranks carbohydrate-containing foods based on how much they increase blood glucose levels after consumption. A food is considered low-GI if its score is 55 or less, medium-GI between 56 and 69, and high-GI if it's 70 or more. The GI score is a valuable tool for managing blood sugar, particularly for individuals with diabetes, but it should be considered alongside other nutritional factors.

The Low-GI Components of Milk

Milk's low GI is a result of several key nutritional components working together to moderate its effect on blood sugar.

Lactose: The natural sugar in milk is lactose, a disaccharide that breaks down into glucose and galactose. Unlike simple sugars like sucrose, lactose is digested more slowly, leading to a more gradual release of glucose into the bloodstream. Lactose itself has a GI of around 46, which is considered moderate, but in the context of milk's other components, the overall GI is lower.
Protein: Milk is a rich source of protein, especially whey protein, which has been shown to stimulate insulin secretion. This insulin response helps transport glucose from the bloodstream into cells, effectively lowering blood sugar levels after a meal. The high protein-to-carbohydrate ratio in milk contributes significantly to its low GI.
Fat: The fat content in milk further slows down the rate of digestion and absorption of carbohydrates. For instance, while whole milk and skim milk have similar carbohydrate counts, the higher fat in whole milk can slow glucose absorption, which impacts the final glycemic response.

Factors that Influence Milk's GI

While whole, skim, and low-fat dairy milk typically have a low GI, the final glycemic effect can be altered by processing, added ingredients, and the presence of other foods in a meal. Factors like added sugars in flavored milks or the breakdown of lactose in lactose-free options can increase the GI. The fat content may also play a role in slowing absorption, although the overall impact is a combination of all macronutrients. Combining milk with other foods, such as high-fiber or protein-rich items, can also influence the glycemic response. Checking nutrition labels is essential to understand the potential impact on blood sugar.

Cow's Milk vs. Plant-Based Alternatives

Plant-based milks have become popular, but their GI can vary significantly depending on their source and ingredients. Comparing them to cow's milk highlights important differences.


Feature	Cow's Milk	Soy Milk	Almond Milk	Oat Milk	Rice Milk
Average GI	Low (30-39)	Low (Around 30)	Low (Varies, often lower GI)	Moderate-High (Around 69)	High (Around 85)
Protein	High	High	Low	Low	Low
Fiber	Very Low	Low	Low	Moderate (contains β-glucan)	Very Low
Fat	Varies (whole, low-fat, skim)	Moderate (healthy fats)	Moderate (healthy fats)	Low	Low
Lactose	Yes	No	No	No	No
Nutrient Fortification	Naturally nutrient-dense	Often fortified	Often fortified	Often fortified	Often fortified

For those seeking low-GI options, unsweetened soy milk and almond milk offer a profile similar to or lower than cow's milk, thanks to their protein and fat content. In contrast, rice milk, and to a lesser extent, oat milk, can have a moderate to high GI due to their carbohydrate structure and low protein and fat content. As always, checking the label for added sugars is critical when assessing the final glycemic impact.

Conclusion

Overall, the GI of milk is low, with values typically ranging from 30 to 39, solidifying its place among foods with a more stable effect on blood sugar. The unique combination of lactose, proteins, and fats in milk facilitates a controlled release of glucose into the bloodstream, making it a beneficial component of a balanced diet, particularly for those managing diabetes or weight. When consuming dairy or plant-based milk alternatives, it is crucial to consider factors like fat content, processing, and added sugars to make the healthiest choice. By understanding these nuances, you can effectively use the glycemic index as a guide for better nutritional choices. For further reading, explore the detailed Glycemic Index database from the University of Sydney to compare specific foods and make informed dietary decisions.

Frequently Asked Questions

The GI of skim milk is approximately 31, which classifies it as a low GI food. Its low GI is largely due to its protein content and the slower digestion of its natural sugar, lactose, despite its lack of fat.

The GI of whole milk is typically around 34, which is very similar to skim milk. While the fat in whole milk can slightly slow down digestion, the carbohydrate content is similar across different types of dairy milk, resulting in a comparable low GI score.

Lactose is digested and absorbed more slowly than other sugars like sucrose, which leads to a more gradual rise in blood glucose. This slow digestion, combined with milk's protein and fat, contributes to milk's overall low glycemic effect.

No, the GI of plant-based milks varies significantly. For example, unsweetened soy and almond milks have a low GI similar to cow's milk, but rice milk and oat milk tend to have a moderate to high GI.

Milk is a suitable choice for diabetics because of its low GI, which helps prevent rapid blood sugar spikes. The protein and fat in milk also assist in stabilizing blood sugar levels, especially when consumed as part of a balanced meal.

The Glycemic Load (GL) considers both the GI and the portion size of a food to determine its total impact on blood sugar. Milk has a low GI and low GL, indicating that even in a typical serving, it has a minimal effect on blood glucose levels.

No, flavored and sweetened milks have added sugars, which significantly increases their GI and GL, making them a less ideal choice for managing blood sugar. It is best to stick to plain, unsweetened versions.