Understanding What is a Level 3 Thickened Diet: IDDSI Liquidised and Moderately Thick

October 14, 2025 •

5 min read

Dysphagia, or difficulty swallowing, affects an estimated 15 million people in the United States alone. For many of these individuals, a modified diet is a crucial safety measure, which is why understanding what is a Level 3 thickened diet is so important for caregivers and patients.

Quick Summary

A Level 3 thickened diet, per the global IDDSI standard, consists of liquidised foods and moderately thick liquids for individuals with swallowing difficulties. It is a smooth, lump-free consistency that requires no chewing and slows the flow of liquids for safer swallowing. A healthcare professional's assessment is needed to prescribe this diet.

Key Points

Definition of IDDSI Level 3: The International Dysphagia Diet Standardisation Initiative (IDDSI) defines Level 3 as moderately thick liquids and liquidised (pureed) foods for individuals with swallowing difficulties.
NDD vs. IDDSI: It's crucial to distinguish IDDSI Level 3 (pureed/liquidised) from the older National Dysphagia Diet (NDD) Level 3, which referred to a different, advanced texture.
Safety from Aspiration: The primary benefit is reduced risk of aspiration pneumonia, as the thicker consistency slows down the bolus and provides more control for those with poor swallowing coordination.
Preparation Techniques: Level 3 liquidised food must be blended until completely smooth with no lumps or seeds, often requiring a sieve. Nutritious liquids like stock or gravy should be used instead of plain water.
Testing for Consistency: Use the IDDSI Flow Test for liquids (at least 8 mL left in a 10 mL syringe after 10 seconds) and the Fork Drip Test for foods (drips in dollops through fork prongs) to ensure safety.
Nutritional Strategy: Due to potential reduced intake, food fortification with high-calorie and high-protein ingredients like powdered milk, cream, or cheese is recommended to prevent malnutrition and weight loss.
Professional Oversight: A speech-language pathologist and a dietitian should always be consulted before starting a thickened diet to ensure it is appropriate, safe, and nutritionally adequate.

What is a Level 3 thickened diet? Understanding IDDSI

When discussing a Level 3 thickened diet, it is critical to refer to the International Dysphagia Diet Standardisation Initiative (IDDSI), which is the current global framework used by healthcare professionals. The IDDSI defines Level 3 as a liquidised food and moderately thick liquid consistency. This clarifies an important point of potential confusion, as a previous standard, the National Dysphagia Diet (NDD), referred to a different texture as Level 3.

In the IDDSI system, Level 3 foods and liquids have specific characteristics:

Liquidised Food: This refers to food that is blended into a completely smooth, lump-free, and homogenous texture. It is moist and cohesive, without any bits of fiber, husks, or seeds. It can be eaten with a spoon but will not hold its shape if spilled on a flat surface.
Moderately Thick Liquid: Drinks at this level are often described as honey-like. They can be consumed from a cup, but flow slowly and require some effort to drink, even through a wide-bore straw.

This diet is typically prescribed for individuals with dysphagia who have poor oral motor control, meaning they struggle with managing thinner liquids or solid foods in their mouth and throat.

Why a thickened diet is crucial for safety

Thickening fluids and modifying food texture is a key strategy for managing dysphagia. The primary goal is to reduce the risk of complications that can arise from swallowing dysfunction.

Reduced Aspiration Risk: The most significant danger of dysphagia is aspiration, where food or liquid enters the airway instead of the esophagus. Thin liquids move very quickly, making them difficult for those with poor swallowing coordination to control. By slowing down the flow of liquids, a moderately thick consistency allows for better control, giving the individual more time to close their airway safely.
Prevention of Pneumonia: When aspirated food or liquid introduces bacteria into the lungs, it can lead to aspiration pneumonia. This is a serious, life-threatening complication, especially for the elderly or immunocompromised individuals. A thickened diet is one of the strategies used to mitigate this risk.
Improved Hydration and Nutrition: Patients with swallowing difficulties may avoid eating and drinking due to anxiety or fear of choking. This can lead to dehydration and malnutrition. A texture-modified diet, when prepared correctly and made appealing, can make it safer and more comfortable for individuals to consume adequate fluids and calories.

How to prepare and test IDDSI Level 3 foods and liquids

Accurate preparation and testing are essential to ensure the safety and effectiveness of a Level 3 diet. The IDDSI provides standardized methods that can be easily performed at home or in a clinical setting.

Preparation Techniques

Use a blender or food processor: All solid foods must be liquidised until completely smooth.
Add nutrient-rich liquids: Instead of just water, blend foods with liquids that add nutritional value, such as gravy, milk, stock, or juices. This prevents dilution of nutrients and adds flavour.
Sieve to remove particles: After blending, pass the mixture through a sieve to remove any remaining lumps, skins, seeds, or fibres.
Use thickeners for liquids: For drinks, use commercially available thickeners to achieve the correct 'moderately thick' consistency. Always follow the product instructions carefully.
Consider food fortification: To boost calories and protein, incorporate ingredients like full-fat dairy, cream, butter, or nut butters into blended foods.

IDDSI Testing Methods

IDDSI Flow Test (for liquids): Use a standard 10 mL syringe. Fill the syringe with the liquid and release it over 10 seconds. For a Level 3 moderately thick liquid, there should be at least 8 mL of liquid remaining in the syringe after 10 seconds.
Fork Drip Test (for food and liquids): Scoop a sample with a fork. A Level 3 liquidised food will drip slowly in dollops through the prongs of the fork. The prongs should not leave a clear pattern on the surface.

Comparison of IDDSI levels

The IDDSI framework covers a continuum of eight levels for food and drinks. Understanding how Level 3 fits into this system can help clarify why this specific modification is necessary.


Feature	IDDSI Level 2: Mildly Thick / Nectar-like	IDDSI Level 3: Moderately Thick / Liquidised	IDDSI Level 4: Extremely Thick / Pureed
Consistency	Easily pourable, flows from a spoon, similar to a thick cream soup.	Flows slowly, can be drunk from a cup, difficult to suck through a straw.	Holds its shape on a spoon or plate, no longer pourable.
Requirement	Can be sipped from a cup, requires some effort with a straw.	Can be taken from a cup or spoon; chewing is not required.	Needs to be eaten with a spoon; no chewing required.
Key Food Examples	Vegetable juices, milkshakes.	Blended soups, smoothies, liquidised meals.	Puddings, custards, mashed potatoes.
IDDSI Test	Flow Test: 4–8 mL remaining in 10 mL syringe after 10 seconds.	Flow Test: At least 8 mL remaining in 10 mL syringe after 10 seconds.	Fork Drip Test: Small amount drips through, holds shape.

Maintaining nutritional health on a Level 3 diet

A Level 3 liquidised diet, while necessary for safety, can pose challenges to adequate nutrition and hydration. Patients often dislike the taste and texture of thickened fluids, which can lead to reduced oral intake. It is vital to take proactive steps to ensure nutritional needs are met.

Here are some tips for maintaining nutritional health:

Maximize calories and protein: Use nourishing liquids for blending and fortification methods. This includes adding ingredients like powdered milk, cream, butter, cheese, or protein supplements to meals.
Prioritize nutrient-dense foods: Ensure every meal is as rich in nutrients as possible. This means blending not just single ingredients, but entire fortified meals, such as a full meal of chicken, vegetables, and gravy.
Offer small, frequent meals: For those with reduced appetite or who tire easily, smaller portions served more frequently throughout the day can help meet daily requirements.
Monitor hydration levels: Thickeners can sometimes contribute to a feeling of fullness, potentially reducing overall fluid intake. Encourage sips of moderately thick fluids throughout the day and track total fluid consumption.
Use visual appeal: Liquidised food can lack visual appeal. To stimulate appetite, use natural food colours to plate separate components of a meal, for instance, a liquidised beef portion next to liquidised carrots and potatoes.

Conclusion: The importance of professional guidance

A Level 3 thickened diet is a crucial intervention for individuals with dysphagia to prevent serious complications like aspiration pneumonia and malnutrition. However, it is a complex modification that requires a tailored approach. The IDDSI framework provides a standardized and clear way to define and test the required consistency for both foods and liquids. Proper preparation and monitoring are essential to ensure both safety and nutritional adequacy.

Any decision to start or change a thickened diet should only be made following a comprehensive assessment by a healthcare team, including a speech-language pathologist and a dietitian. These specialists can provide guidance on the specific level required, safe preparation techniques, and strategies for maintaining optimal nutrition and hydration. Following their recommendations is the safest path forward for anyone requiring this modified diet.

For more information on the official guidelines, consult the International Dysphagia Diet Standardisation Initiative's website. [https://iddsi.org/standards/framework/]

Frequently Asked Questions

The IDDSI framework is the current global standard. IDDSI Level 3 refers to liquidised foods and moderately thick liquids. In contrast, the older National Dysphagia Diet (NDD) Level 3 described advanced foods, which were soft, moist, and bite-sized. This is a crucial distinction that must be followed as per your healthcare provider's recommendations.

Not thickening liquids can lead to serious complications. The quick flow of thin liquids increases the risk of aspiration (inhaling liquid into the lungs), which can cause aspiration pneumonia, and can also result in dehydration and malnutrition.

Yes, but with effort. Moderately thick liquids (IDDSI Level 3) require some effort to drink, even through a wide-diameter straw, due to their viscosity. Thinner liquids are not recommended, and for very thick liquids (Level 4), straws should not be used.

You can use the IDDSI Fork Drip Test. Scoop the food with a fork; if it is the correct Level 3 liquidised consistency, it will drip slowly through the prongs in dollops and not hold its shape.

Yes, many regular foods can be blended to achieve a Level 3 consistency. However, you must add extra liquids, such as gravy, milk, or stock, and sieve the final product to remove any lumps, skins, or seeds. Water is generally not recommended as it reduces the nutritional value.

To prevent malnutrition, fortify meals and drinks with high-calorie, high-protein ingredients like powdered milk, cream, melted cheese, or butter. Offering small, frequent meals throughout the day and prioritizing nutrient-dense foods is also important.

Any liquid can be thickened to a moderately thick (Level 3) consistency using commercial thickeners. This includes juice, coffee, tea, and milkshakes. Some smoothies can also be appropriate if blended completely smooth and tested for the right thickness.