Nutrition Diet: How much lactose is in 1 glass of milk?

October 17, 2025 •

4 min read

A single glass (approximately 250ml) of regular cow's milk contains about 12 to 16 grams of lactose, regardless of its fat content. Understanding how much lactose is in 1 glass of milk is an essential first step for anyone managing dietary sensitivities, especially those with lactose intolerance.

Quick Summary

An exploration of the lactose content in various types of cow's milk and dairy products. The article covers the causes and symptoms of lactose intolerance, offers strategies for managing intake, and compares a range of dairy and plant-based milk alternatives.

Key Points

Lactose Content: A standard 250ml (1 cup) glass of cow's milk contains 12-16 grams of lactose, consistently across fat levels.
Lactase Deficiency: Lactose intolerance is caused by insufficient lactase enzyme, not a milk allergy, and its severity varies by individual.
Symptom Management: Spreading out dairy intake and consuming it with other foods can help manage symptoms for people with moderate intolerance.
Diverse Alternatives: Options include lactose-free milk with added lactase or plant-based milks like soy, almond, and oat, which have 0 grams of lactose.
Reading Labels: Check ingredient lists for hidden lactose, especially in processed foods, using terms like 'milk solids' and 'whey'.
Tolerance Varies: Many people with lactose intolerance can tolerate small amounts of dairy, and hard cheeses or yogurt often contain much less lactose.

What is Lactose and Where Does it Come From?

Lactose is a type of sugar naturally found in milk and other dairy products. It is a disaccharide, meaning it is composed of two smaller sugar molecules: glucose and galactose. In a healthy digestive system, an enzyme called lactase, produced in the small intestine, breaks down lactose into these two simpler sugars, which are then absorbed by the body. For individuals with a deficiency of this enzyme, consuming lactose can lead to digestive discomfort.

The Lactose Content of Cow's Milk

For a standard 250ml (approximately 1 cup) serving, the lactose content in cow's milk is surprisingly consistent across different fat percentages. The fat content does not significantly alter the amount of lactose present in the milk. This is a common misconception, but the carbohydrates (sugars) and fat are separate components of the milk. Therefore, whether you choose whole milk, 2% milk, or skim milk, the lactose level per glass remains in a similar range of 12 to 16 grams. For example, studies have shown that 250ml of full-cream milk contains about 15.75g of lactose, while the same amount of skim milk contains around 12.5g.

Understanding Lactose Intolerance

Lactose intolerance is not a food allergy but a digestive condition caused by a lack of the lactase enzyme. When undigested lactose reaches the large intestine, gut bacteria ferment it, producing gases and other byproducts. This process is what triggers the uncomfortable symptoms associated with lactose intolerance. The severity of symptoms can vary widely among individuals, depending on the degree of lactase deficiency and the amount of lactose consumed. The symptoms typically appear within 30 minutes to 2 hours after consuming lactose-containing foods.

Common Symptoms of Lactose Intolerance

Bloating and abdominal cramps
Excessive gas (flatulence)
Diarrhea
Nausea, and sometimes, vomiting
Stomach rumbling or gurgling

Managing Lactose Consumption

For those with lactose intolerance, it is not always necessary to completely eliminate dairy from your diet. Many individuals can tolerate small amounts of lactose, and strategic dietary choices can help manage symptoms effectively.

Moderation is key: Most people with lactose intolerance can tolerate up to 12 grams of lactose (the amount in about one cup of milk) at a time, especially if consumed with other foods.
Pair with other foods: Consuming milk alongside a meal can slow down the digestive process, giving the body more time to break down the lactose and potentially reducing symptoms.
Choose low-lactose dairy: Some dairy products naturally contain less lactose. Aged, hard cheeses like cheddar and parmesan, and most yogurts, have significantly less lactose than milk.
Consider lactase supplements: Over-the-counter lactase enzyme supplements can be taken before consuming dairy to help your body digest lactose.

Dairy and Plant-Based Milk Alternatives

For those who need to avoid lactose completely or prefer non-dairy options, the market offers a wide array of alternatives. Lactose-free cow's milk is a popular option; it is regular cow's milk that has the lactase enzyme added to break down the lactose. For a completely dairy-free approach, plant-based milks offer different nutritional profiles and tastes.

Comparison of Milk Types


Product	Lactose Content per 250ml	Protein per 250ml	Calcium per 250ml
Regular Cow's Milk	12-16g	~8g	~300mg
Lactose-Free Milk	~3g	~8g	~300mg
Soy Milk (Fortified)	0g	~8g	~300mg
Almond Milk (Fortified)	0g	~1.4g	~300mg
Oat Milk (Fortified)	0g	~2.1g	~300mg

Note: Nutritional values for fortified plant-based milks can vary by brand, so always check the label.

Reading Food Labels for Lactose

When monitoring lactose intake, it is crucial to read food labels carefully, as lactose can be hidden in unexpected places. The ingredient list will indicate the presence of dairy-based ingredients. Ingredients to look out for include:

Milk solids
Non-fat milk solids
Whey
Milk sugar

While this is especially important for those with severe sensitivities, most processed foods contain low levels of lactose that are well-tolerated by individuals with mild to moderate intolerance.

Conclusion

The lactose content in a single glass of cow's milk is consistent, typically falling between 12 and 16 grams. This information is key for individuals with lactose intolerance, a common condition caused by a lactase enzyme deficiency. By understanding the amount of lactose in milk, recognizing their personal tolerance levels, and exploring the wide range of available low-lactose or lactose-free alternatives, managing a healthy and comfortable diet is very achievable. Whether opting for lactose-reduced dairy or switching to a plant-based alternative, there are many ways to ensure proper nutrition while avoiding digestive distress. For those with persistent digestive concerns, consulting a healthcare professional is always recommended for a proper diagnosis and tailored advice.

For more information on lactose intolerance and dietary management, you can refer to the National Institutes of Health.

Frequently Asked Questions

The lactose content is very similar. A 250ml serving of either whole or skim cow's milk contains approximately 12 to 16 grams of lactose, as the fat content does not significantly affect the sugar content.

Many individuals with lactose intolerance can tolerate a small amount of milk, typically up to 12 grams of lactose (about one glass) at a time, especially if consumed with other food to slow digestion.

No. Aged hard cheeses, like cheddar and parmesan, contain very little lactose because the bacteria used in the aging process consume most of it. Yogurts also have less lactose than milk, as the cultures break it down.

You can check the ingredient list for ingredients like milk solids, whey, milk powder, or lactose. For manufactured lactose-free products, the label will typically state 'lactose-free'.

Several plant-based milks are naturally lactose-free and include soy, almond, oat, and rice milk. For a dairy-based option, lactose-free cow's milk is widely available.

The lactase enzyme's role is to break down lactose into the simple sugars glucose and galactose, which can then be absorbed by the body. A deficiency of this enzyme is what causes lactose intolerance.

Yes, over-the-counter lactase enzyme supplements can be taken right before eating or drinking dairy products to assist your body in digesting lactose and reducing symptoms.