What are Monosaccharides and Disaccharides Also Referred to as? A Guide to Simple Sugars

December 8, 2025 •

3 min read

Carbohydrates are essential macronutrients, and a key fact is that all dietary sugars, including monosaccharides and disaccharides, are often called simple carbohydrates. These molecules serve as the body's primary energy source, fueling various metabolic processes.

Quick Summary

Monosaccharides are simple sugars, and disaccharides are double sugars, both of which fall under the category of simple carbohydrates and are rapidly digested.

Key Points

Simple and Single Sugars: Monosaccharides are known as simple or single sugars because they consist of only one sugar unit.
Double Sugars: Disaccharides are referred to as double sugars, as they are formed from two monosaccharide units joined together.
Simple Carbohydrates: Monosaccharides and disaccharides are collectively called simple carbohydrates due to their small size and quick absorption.
Quick Energy Source: Because of their simple structure, these sugars are digested rapidly, leading to a quick rise in blood sugar for immediate energy.
Building Blocks: Monosaccharides like glucose are the basic building blocks for forming larger carbohydrates, including disaccharides and polysaccharides.
Digestive Breakdown: Disaccharides, such as sucrose and lactose, must be broken down by specific enzymes into their constituent monosaccharides before the body can use them.

The Chemical Classification of Sugars

Within the field of biochemistry, monosaccharides and disaccharides are chemically classified based on their structure. The term 'saccharide' is derived from the Greek word for sugar. The prefix 'mono-' means one, indicating a single sugar unit, while 'di-' means two, indicating two sugar units bonded together. It is this fundamental difference in their molecular size that dictates their common names and how the body processes them.

Monosaccharides: The 'Simple' and 'Single' Sugars

Monosaccharides, as their name suggests, are the simplest form of sugar and the fundamental building blocks of all carbohydrates. They cannot be broken down further by hydrolysis. For this reason, they are commonly referred to as simple sugars or single sugars. They are readily absorbed by the body for quick energy.

Key examples of monosaccharides include:

Glucose (dextrose): Often called 'blood sugar,' it is the most important monosaccharide and the primary source of energy for the body's cells.
Fructose (levulose): Known as 'fruit sugar,' it is the sweetest of all sugars and is found naturally in fruits, honey, and some vegetables.
Galactose: Found most often as part of the disaccharide lactose (milk sugar).

Disaccharides: The 'Double' Sugars

Disaccharides are carbohydrates formed when two monosaccharide units join together via a glycosidic bond in a process called dehydration synthesis, or condensation reaction. Because of this structure, they are often called double sugars. Disaccharides must be broken down into their individual monosaccharide units by enzymes before they can be absorbed by the body.

Common disaccharides include:

Sucrose: Composed of one glucose and one fructose molecule, it is the familiar 'table sugar' derived from sugarcane or sugar beets.
Lactose: Made of one glucose and one galactose molecule, it is the 'milk sugar' found in dairy products.
Maltose: Formed by two glucose molecules, it is often called 'malt sugar' and is produced during the breakdown of starches.

Simple Carbohydrates: The Collective Term

When grouping monosaccharides and disaccharides together, the most common collective term is simple carbohydrates. This distinguishes them from more complex carbohydrates, like polysaccharides (e.g., starches and fiber), which are long chains of many sugar units and take longer for the body to digest. The American Heart Association notes that simple carbs, due to their quick digestion, provide rapid energy, while complex carbs offer a slower, more sustained release of glucose.

Comparison of Monosaccharides and Disaccharides


Feature	Monosaccharides	Disaccharides
Alternate Names	Simple sugars, single sugars	Double sugars
Structural Units	One sugar unit	Two sugar units
Absorption	Can be absorbed directly into the bloodstream	Must be broken down by enzymes into monosaccharides first
Hydrolysis	Cannot be hydrolyzed further	Can be hydrolyzed into two monosaccharides
Examples	Glucose, Fructose, Galactose	Sucrose, Lactose, Maltose
Occurrence	Found freely in fruits, honey, and bloodstream	Common in table sugar, milk, and malt products

Importance of Simple Sugars in the Body

The rapid digestion and absorption of simple carbohydrates are what make them a quick source of fuel for the body. When simple sugars enter the bloodstream, they cause a rapid increase in blood sugar levels, triggering the pancreas to release insulin. Insulin helps transport the sugar from the blood into the cells to be used for immediate energy. This quick energy boost is beneficial in certain situations, such as for athletes during intense exercise. However, excessive consumption of simple carbs, especially added sugars, can lead to negative health effects, including weight gain and an increased risk of type 2 diabetes and cardiovascular issues over time. For better health, it's recommended to consume natural simple sugars found in fruits and milk, which also provide beneficial nutrients and fiber, and to prioritize complex carbohydrates for sustained energy. Learn more about the biology of carbohydrates from reliable sources such as the National Institutes of Health.

Conclusion

In summary, monosaccharides are also called simple or single sugars, and disaccharides are known as double sugars. Together, both types are categorized as simple carbohydrates, in contrast to the more complex polysaccharides. Understanding these different names and classifications provides clarity on how these essential biomolecules function within our body and contributes to informed dietary choices for better health and sustained energy.

Frequently Asked Questions

Simple carbohydrates are monosaccharides and disaccharides, which are small sugar molecules that the body digests quickly for immediate energy. Complex carbohydrates are polysaccharides, which are large, long chains of sugar units that are digested more slowly and provide sustained energy.

No, not all simple sugars are bad. Simple sugars found naturally in whole foods like fruit and milk also contain vitamins, minerals, and fiber. However, simple sugars from highly processed foods or added sugars lack these nutrients and are less healthy when consumed in large amounts.

Glucose, a monosaccharide, is also commonly referred to as dextrose or blood sugar. It is the body's primary fuel source and is found circulating in the bloodstream.

The body uses specific enzymes called disaccharidases, such as lactase and sucrase, to break down disaccharides into their simpler monosaccharide units during digestion in the small intestine.

The collective term for both monosaccharides and disaccharides is 'simple carbohydrates.' This is a broad classification often used in nutrition to differentiate them from complex carbohydrates like starch and fiber.

All monosaccharides are considered reducing sugars because they possess a free aldehyde or ketone group that allows them to act as a reducing agent in a chemical reaction, such as reducing copper(II) sulfate.

Yes, the body can produce its own glucose, a monosaccharide, through a process called gluconeogenesis, particularly when there is a lack of carbohydrate intake.