What Level of Iddsi is Thickened Fluids?

November 19, 2025 •

4 min read

The International Dysphagia Diet Standardisation Initiative (IDDSI) framework classifies thickened liquids across four specific levels, from Levels 1 to 4. The proper classification is crucial for individuals with swallowing difficulties, or dysphagia, to ensure safety and prevent health complications like aspiration pneumonia. Understanding exactly what level of IDDSI is thickened fluids is the first step toward effective dietary management.

Quick Summary

The IDDSI framework classifies thickened fluids from Level 1 (Slightly Thick) to Level 4 (Extremely Thick), defining their consistency and appropriate consumption methods. It replaces older terms like nectar-thick and honey-thick with a standardized, globally consistent system to improve patient safety. The correct level is determined by a healthcare professional based on individual needs.

Key Points

Thickened Fluid Categories: The IDDSI framework categorizes thickened liquids into Levels 1 (Slightly Thick), 2 (Mildly Thick), 3 (Moderately Thick), and 4 (Extremely Thick).
Level 1 (Slightly Thick): Flows like water but with some drag, similar to apricot nectar, and leaves 1-4 mL in a 10mL syringe flow test.
Level 2 (Mildly Thick): Nectar-like consistency that pours off a spoon, leaving 4-8 mL in a 10mL syringe flow test.
Level 3 (Moderately Thick): Honey-like, pours slowly in dollops, and leaves >8 mL but <10 mL in a 10mL syringe flow test.
Level 4 (Extremely Thick): Pudding-like, holds its shape, and must be eaten with a spoon; the syringe flow test shows no flow.
Testing Methods: The IDDSI Flow Test using a 10 mL syringe is the standard method for confirming liquid thickness levels.
Dysphagia Management: Choosing the correct IDDSI level is critical for managing dysphagia safely and preventing aspiration.
Healthcare Guidance: Recommendations for thickened liquids should come from a qualified healthcare professional, such as a speech-language pathologist.

A Guide to the IDDSI Thickened Fluid Levels

For individuals with swallowing impairments, or dysphagia, the texture of food and drink is modified to prevent choking and aspiration. The International Dysphagia Diet Standardisation Initiative (IDDSI) has established a framework that provides a universal language for these texture modifications. Unlike the previous, often inconsistent, naming conventions, the IDDSI levels for liquids—Level 1 (Slightly Thick), Level 2 (Mildly Thick), Level 3 (Moderately Thick), and Level 4 (Extremely Thick)—are defined using simple, accessible tests. This standardization is vital for both caregivers and healthcare professionals to ensure consistency and patient safety across different care settings.

Understanding the Specific IDDSI Liquid Levels

Level 1: Slightly Thick. This is the first level of thickening. These liquids are thicker than water but can still be drunk through a straw with a little more effort. Some commercially available anti-regurgitation formulas may be at this consistency. The IDDSI Flow Test for this level should leave between 1 and 4 mL of fluid in a 10 mL syringe after 10 seconds.
Level 2: Mildly Thick. Often described as nectar-like, these liquids flow off a spoon but slower than unthickened drinks. They can be sipped from a cup and require some effort to drink through a standard bore straw. The IDDSI Flow Test for this level will leave between 4 and 8 mL in the syringe after 10 seconds.
Level 3: Moderately Thick. Formerly known as honey-thick, these liquids are thicker and can be drunk from a cup but are difficult to sip through a straw. They pour slowly from a spoon in dollops. An IDDSI Flow Test will leave more than 8 mL but less than 10 mL of liquid in the syringe after 10 seconds. Level 3 also includes pureed foods.
Level 4: Extremely Thick. With a consistency similar to pudding, these liquids hold their shape and cannot be sucked through a straw. They must be eaten with a spoon. A spoon tilt test shows the liquid falling off in a cohesive lump. In the IDDSI Flow Test, the syringe will remain full, with no flow or drip. Level 4 also includes pureed foods.

How to Verify IDDSI Levels

To ensure liquids are at the correct consistency, the IDDSI provides simple testing methods accessible to caregivers. The primary method for liquids is the IDDSI Flow Test, which uses a standard 10 mL slip-tip syringe.

Remove the plunger from the syringe and cover the tip with a finger.
Fill the syringe to the 10 mL line with the liquid to be tested.
Simultaneously release your finger and start a stopwatch for 10 seconds.
After 10 seconds, cover the tip again and measure the amount of liquid remaining.
Compare the remaining volume to the IDDSI chart to determine the level.

For liquids at Level 3 and 4, which are too thick for the syringe test, the Fork Drip Test or Spoon Tilt Test are used. These qualitative methods provide a practical way to check consistency without specialized equipment.

Comparison of IDDSI Thickened Liquid Levels


Feature	IDDSI Level 1 (Slightly Thick)	IDDSI Level 2 (Mildly Thick)	IDDSI Level 3 (Moderately Thick)	IDDSI Level 4 (Extremely Thick)
Former NDD Name	Natural Nectar	Nectar-Thick	Honey-Thick	Pudding-Thick
Consistency	Thicker than water; flows easily	Pours quickly from spoon; visible body	Pours slowly; drips in dollops	Holds shape; not pourable
Consumption	Cup or straw	Cup; straw with effort	Cup with effort; difficult with straw	Spoon only
IDDSI Flow Test	1–4 mL remaining after 10s	4–8 mL remaining after 10s	>8–<10 mL remaining after 10s	10 mL remaining; no flow
Typical Examples	Some fruit nectars, apricot juice	Creamy soup, thick chocolate milk	Honey, some yogurts	Pudding, thick milkshake

The Importance of Correct Thickening

Prescribing and adhering to the correct IDDSI level is vital for managing dysphagia. Incorrectly prepared or chosen liquid consistencies can lead to serious health issues. A liquid that is too thin for a person's swallowing ability can result in aspiration, where the liquid enters the lungs. Conversely, a liquid that is too thick can lead to dehydration, poor palatability, and increased effort during swallowing, which can be exhausting for the patient. Compliance with thickened liquid diets is a known challenge, and providing the safest, least restrictive consistency is the goal of a healthcare team. Speech-language pathologists and dietitians are key members of this team who evaluate and recommend the appropriate IDDSI level for each individual.

Conclusion

Thickened fluids are precisely classified into IDDSI Levels 1, 2, 3, and 4, ranging from slightly thick to extremely thick. This standardized system, validated by simple flow and consistency tests, replaces older, ambiguous terminology. The appropriate level is determined by a healthcare professional based on a patient's specific swallowing needs to ensure safety and hydration. Consistent application of these levels helps to prevent health complications like aspiration while improving overall nutrition and quality of life for individuals with dysphagia.

IDDSI: The International Dysphagia Diet Standardisation Initiative

Frequently Asked Questions

IDDSI Level 2 is classified as 'Mildly Thick' and is comparable to a nectar-like or creamy soup consistency. It flows quickly off a spoon but takes some effort to drink through a standard straw, and leaves 4-8 mL in a 10 mL syringe flow test.

Under the older National Dysphagia Diet (NDD) framework, IDDSI Level 3 liquids were referred to as 'honey-thick' liquids. These are now standardized as 'Moderately Thick' liquids under the IDDSI system.

In the IDDSI framework, an extremely thick fluid is classified as Level 4. It has a pudding-like consistency, holds its shape, cannot be sipped from a cup or straw, and must be eaten with a spoon.

The primary method for testing liquid thickness is the IDDSI Flow Test, which uses a 10 mL syringe. The amount of liquid remaining in the syringe after 10 seconds is used to determine the correct IDDSI level.

Using the correct IDDSI level is crucial for safety, especially for individuals with dysphagia. Incorrectly thickened liquids can lead to aspiration (fluid entering the lungs) if too thin, or dehydration if too thick and difficult to consume.

No, the IDDSI framework distinguishes between food and drink levels, although some levels overlap. It is possible for a person to require different IDDSI levels for different items, such as Level 4 for food and Level 2 for liquids.

For babies, IDDSI Level 1 (Slightly Thick) is typically used if they have swallowing issues with thin liquids. These liquids are thicker than water but can still flow through a bottle nipple.