IDDSI Level 2 Mildly Thick Liquids: Clinical Indications, Flow Test and Preparation

IDDSI Level 2 — Mildly Thick (colour: pink) — is the lightest level of thickened liquid in the International Dysphagia Diet Standardisation Initiative (IDDSI) framework. It is the most commonly prescribed thickened liquid level in dysphagia management and often the first step away from thin liquids for patients who aspirate water.

Understanding when Level 2 is clinically appropriate, how to prepare it correctly, and how to verify it at the point of use is essential for clinicians, care home kitchen staff, and family caregivers.

This article is consistent with the IDDSI 2019 framework and follows ASHA Practice Portal guidance on adult dysphagia.

What Is IDDSI Level 2 Mildly Thick?

The IDDSI defines Level 2 (Mildly Thick) liquids by their physical flow properties:

• Thicker than water, but flows freely off a spoon
• Can be drunk from a cup, glass, or teacup in the normal way (the patient does not need to tilt the cup excessively)
• Flows more slowly than thin liquid (Level 0) but faster than Level 3 (Moderately Thick)
• Does not hold its shape; pours in a continuous stream
• No lumps or particles

The original terminology that Level 2 replaces varies by country and institution:

• Australia: “mildly thick” (NDDSC pre-IDDSI)
• USA/Canada: “nectar thick” (NDD pre-IDDSI)
• UK: “Stage 1” (NPSA pre-IDDSI) — now deprecated
• Hong Kong hospital-specific: terms varied; now all public hospitals use IDDSI

The global shift to IDDSI has eliminated these inconsistencies. A “Level 2 Mildly Thick” prescribed in a Hong Kong public hospital should be understood identically by a private residential care home kitchen.

Who Needs Level 2 Mildly Thick?

Level 2 is prescribed by an SLT following objective assessment (VFSS or FEES) that demonstrates:

• Aspiration of thin liquids (Level 0) — confirmed by videofluoroscopy or FEES
• Penetration of thin liquids that is not self-cleared — material entering the laryngeal vestibule without effective cough response
• Delayed swallow initiation — thin liquids enter the pharynx before the swallow reflex triggers; Level 2 slows the flow enough to allow the reflex to fire before the bolus reaches the open airway

Common clinical conditions where Level 2 is frequently prescribed:

• Post-stroke dysphagia with delayed pharyngeal swallow initiation
• Parkinson’s disease dysphagia (ON period — during OFF periods, Level 3 may be needed)
• Presbyphagia with subclinical aspiration on thin liquids in frail older adults
• Post-COVID or post-extubation dysphagia during recovery phase

Level 2 is chosen over Level 3 when:

• The physiological deficit is mild (brief delay in swallow trigger, not absent trigger)
• VFSS/FEES shows aspiration on Level 0 but safety on Level 2
• Palatability and patient acceptance are prioritised

Some patients require Level 3 or Level 4 if Level 2 remains unsafe. The IDDSI level prescription must be individually determined by the SLT; it should never be self-prescribed.

The IDDSI Flow Test

The IDDSI flow test is the standardised method for verifying that a thickened liquid is at the correct level. It requires:

Equipment:

• IDDSI 10 mL syringe (available from IDDSI-compliant suppliers)
• 10 seconds to time the test
• A clean flat surface or container

Procedure:

1. Fill the syringe to exactly 10 mL with the prepared thickened liquid
2. Hold the syringe vertically, with your thumb over the top
3. Remove your thumb and allow the liquid to flow freely for exactly 10 seconds
4. At exactly 10 seconds, place your thumb back over the top to stop the flow
5. Read the volume remaining in the syringe

Interpretation:

For Level 2, the target is 1–4 mL remaining after 10 seconds.

If >4 mL remains, the liquid is too thick (Level 3) — add more liquid and retest. If <1 mL remains, the liquid is too thin — add more thickener and retest.

Preparing Level 2 Mildly Thick: Common Thickeners

Starch-Based Thickeners (e.g., Thick-It, various HK brands)

Starch thickeners use modified cornstarch or rice starch to increase viscosity. They are widely available, relatively inexpensive, and suitable for hot and cold drinks.

Considerations:

• Viscosity increases over time after preparation — the drink may become thicker than intended if it sits for 15–30 minutes; IDDSI flow test at point of serving (not at point of preparation)
• May alter the taste and appearance of drinks; some patients find them unpalatable
• Suitable for: water, juice, cold tea, soup broth

Typical dose for Level 2: follow manufacturer’s instructions per 200 mL liquid; verify with IDDSI flow test.

Gum-Based Thickeners (e.g., Nutilis Clear, Thick & Easy Clear)

Gum-based thickeners use xanthan gum as the gelling agent. They have several advantages:

• Clarity — do not make drinks cloudy (preferred by many patients and families)
• Stable viscosity — do not continue to thicken over time; more consistent for institutional preparation
• No starchy aftertaste
• Suitable for hot and cold drinks

In Hong Kong, gum-based thickeners are available from healthcare distributors and increasingly from pharmacies. They are often more expensive than starch-based products but produce more consistent results.

Practical Tips for Level 2 Preparation

• Always use the IDDSI flow test before serving — particularly important when a new thickener batch is opened or when a different staff member prepares drinks
• Label thickened drinks clearly — use IDDSI colour-coded labels (pink for Level 2) on drink containers in residential care kitchens
• Prepare fresh for each meal — particularly for starch-based thickeners that continue to thicken over time
• All drinks are thickened — unless the SLT report specifically states certain drinks are safe at Level 0 (rare), every drink including water, tea, medication water, and oral supplement must be at the prescribed IDDSI level
• Medications: check with the pharmacist whether medications dissolved in water should be given at Level 2; most oral liquid medications can be safely administered with Level 2 thickened water; do not crush tablets and add to thickened liquid without pharmacy advice

Patient Acceptance and Adherence

Compliance with thickened liquids is a documented clinical challenge — some studies report that up to 50% of patients prescribed thickened liquids do not adhere to the prescription, often drinking thin liquids covertly. Reasons include taste, texture, and loss of enjoyment of favourite drinks.

Where possible, use naturally thick liquids as alternatives to artificially thickened water:

• Mango juice — naturally near Level 2 viscosity (verify with flow test)
• Nectars — apricot, guava, and tomato nectars often sit at Level 2 without added thickener
• Milk — whole milk typically falls in Level 1–2 range

The HKU Swallowing Research Lab (Prof. Karen Chan) has noted that Cantonese patients’ preferences for specific drinks — chrysanthemum tea, soy milk, rice water — should be incorporated into thickening plans to improve adherence. A culturally responsive thickening plan is more likely to be followed.

For information on IDDSI levels and the full framework, see iddsi.org/framework. For referral guidance, see When to Refer to a Speech and Language Therapist.

References

1. American Speech-Language-Hearing Association. Adult Dysphagia Practice Portal. https://www.asha.org/practice-portal/clinical-topics/adult-dysphagia/
2. National Institute for Health and Care Excellence. Stroke Rehabilitation in Adults (CG162). https://www.nice.org.uk/guidance/cg162
3. IDDSI. The IDDSI Framework. https://www.iddsi.org/framework
4. Logemann JA, et al. (2015). Disorders of deglutition. Handbook of Clinical Neurology, 129, 465–487. PMID: 26315994