Dysphagia Knowledge Hub — 吞嚥困難知識庫

IDDSI Level 2 (Mildly Thick): Flow Test, Clinical Indications, Thickener Selection, and Caregiver Guidance

What Is IDDSI Level 2?

IDDSI Level 2, designated Mildly Thick, is the second tier of liquid modification above thin liquids. A Level 2 liquid flows perceptibly more slowly than water and has a slightly syrup-like quality. It requires a small but noticeable effort to drink from a cup or straw. In the IDDSI framework, Mildly Thick occupies the range between Level 1 (Slightly Thick) and Level 3 (Liquidised), and it is one of the most commonly prescribed liquid levels in dysphagia management internationally.

Level 2 is sometimes informally referenced as the successor to the old “nectar thick” or “Stage 2” designations used before IDDSI was adopted, but the two systems do not map precisely. Clinicians transitioning from pre-IDDSI terminology should always verify current prescriptions against IDDSI flow test values.

Syringe Flow Test: Level 2 Values

Level 2 result: 4–8 mL remaining in the syringe after 10 seconds.

Test procedure recap:

Use a standard, clean 10 mL catheter-tip syringe.
Draw 10 mL of liquid at serving temperature.
Hold vertically with tip pointing down.
Release plunger, allow free flow for exactly 10 seconds.
Read remaining volume.

If under 4 mL remains, the liquid is Level 1 or Level 0 — under-thickened. If over 8 mL remains, the liquid has reached Level 3 (Liquidised) — over-thickened, which carries its own clinical risks including increased effort, fatigue, and reduced fluid intake.

The 4–8 mL window is wider than Level 1’s 1–4 mL range, giving slightly more preparation tolerance, but temperature sensitivity remains clinically relevant. Starch-based thickeners tested at room temperature frequently test at a higher viscosity when chilled, meaning a Level 2 liquid prepared at room temperature may behave as Level 3 when refrigerated and re-served.

Clinical Rationale: Who Benefits from Level 2?

Level 2 is appropriate when thin liquids are confirmed aspirated and Level 1 has been shown (by instrumental or clinical assessment) to be insufficient to protect the airway. It is the most commonly prescribed thickening level in post-stroke and neurodegenerative disease management.

Moderate pharyngeal dysphagia. Patients with moderately reduced laryngeal elevation, incomplete epiglottic retroflexion, or delayed pharyngeal swallow trigger benefit from the additional resistance Level 2 provides. The slower bolus transit gives the pharyngeal musculature more time to complete the swallow sequence before material reaches the laryngeal inlet.

Post-stroke patients with persistent aspiration. In acute stroke units and rehabilitation wards, Level 2 is a frequent first-line prescription after thin-liquid aspiration is identified on bedside assessment. It is then re-evaluated as swallowing function recovers.

Parkinson’s disease with progressive dysphagia. As Parkinson’s advances, pharyngeal wall motion weakens and cricopharyngeal dysfunction may develop. Level 2 thickening combined with postural manoeuvres (chin tuck, head rotation) is a common combination strategy.

Head and neck cancer during and after radiotherapy. Radiation-induced fibrosis of the pharyngeal constrictors and suprahyoid muscles can severely impair swallowing. Level 2 may be part of a modified diet protocol during and after treatment, alongside rehabilitation exercises.

Level 2 should never be self-prescribed by a caregiver or patient without professional assessment. Aspiration of thickened liquids also occurs — particularly in patients with severely reduced pharyngeal sensation — and the prescription of Level 2 does not eliminate aspiration risk in all cases.

Allowed and Excluded Items at Level 2

Level 2 applies to liquids only. Semisolid foods — even thin purees — fall under food texture levels (3–7) and are assessed separately.

Liquids typically achievable at Level 2 with thickener:

Water, fruit juices, cordials, tea, coffee — all require thickener added to specified dose
Milk (both dairy and plant-based) — requires thickener; note that milk proteins interact with some thickener formulations
Warm soups (clear broth, miso-type) — strained only, no solids; require thickening
Oral nutritional supplement drinks — may reach Level 2 at standard concentration with added thickener, or check manufacturer IDDSI certification

Items that do not belong at Level 2 without testing:

Smoothies and blended fruit drinks — viscosity varies enormously by ingredient and blending time; must be syringe-tested per batch
Commercial “nectar” drinks — unless IDDSI-certified Level 2, the old nectar designation is not equivalent
Coconut milk drinks — high natural viscosity but inconsistent; test each batch

Items not appropriate at any liquid level:

Any drink with particulates, pulp, or suspended solids — these create mixed-texture risk even in thickened form
Carbonated drinks — carbonation affects viscosity measurement and is not recommended with most thickeners

Thickener Selection: Starch vs. Xanthan Gum

Two main thickener chemistries are used clinically:

Starch-based thickeners: Less expensive, widely available, but temperature-unstable. They continue to thicken after preparation (reaching peak viscosity 10–15 minutes post-mixing), thin when heated, and thicken when chilled. They are also broken down by amylase in saliva, meaning that a drink thickened to Level 2 may thin significantly when held in the mouth for extended periods — a concern in patients with slow oral processing.

Xanthan gum-based thickeners: More temperature-stable, more resistant to salivary amylase, and tend to maintain viscosity more consistently across preparation and storage. They are generally preferred for clinical prescriptions where precision and consistency are required, though they are more expensive.

When switching brands or formulations, always recalculate the dose and verify with a syringe test before implementing.

Common Caregiver Errors at Level 2

Mixing thickener before adding to hot liquids. Some thickeners form lumps when added to very hot liquid. Follow manufacturer instructions for mixing sequence. For hot teas and soups, allow liquid to cool to approximately 70 degrees Celsius before adding thickener and mix immediately.

Over-thickening as a safety buffer. Caregivers sometimes reason that if Level 2 is the prescription, thickening further makes things safer. It does not. Over-thickening increases swallowing effort, increases residue in the pharynx, reduces fluid intake from reduced palatability, and may paradoxically increase aspiration risk in patients with pharyngeal weakness.

Not re-testing after the drink has been standing. A Level 2 drink tested immediately after preparation may drift to Level 3 over 20–30 minutes as starch-based thickeners continue to hydrate. Either use xanthan gum-based products or serve immediately after preparation.

Discarding leftover thickened drinks and remaking incorrectly. In ward and care home settings, staff frequently remake thickened drinks without measuring thickener by weight or volume. Estimating “a scoop” without a standardised scoop leads to dose variation of up to 50% across different staff members.

HK and International Food and Drink Examples

Common HK beverages thickened to Level 2:

Chrysanthemum tea — popular with elderly in Hong Kong; thickened for patients in residential care
Warm barley water — already slightly viscous naturally; requires syringe test before assuming compliance
Thickened red bean soup — only if fully strained with no solids; texture of any suspended solids would disqualify it from being a pure liquid prescription
Thickened soy milk at Level 2 dose — commonly used in elderly care centres in HK

International examples:

Thickened Ensure or Fortisip at Level 2 dose — widely used in hospital and nursing home settings
Thickened apple, grape, or cranberry juice — common in North American and Australian residential care
Thickened oral rehydration solutions — used in paediatric dysphagia management

Documentation and Communication

Use the full IDDSI designation: Level 2 / Mildly Thick. Avoid legacy terms including “nectar thick,” “Stage 2,” or “medium thick” — none of these reliably map to Level 2 under IDDSI testing criteria. All handover documents, diet orders, nursing care plans, and family instruction sheets should carry the IDDSI level number and descriptor together.

Summary

IDDSI Level 2 (Mildly Thick) is the most widely prescribed thickened liquid level in dysphagia management. The syringe flow test target is 4–8 mL remaining at 10 seconds. It is indicated for moderate pharyngeal dysphagia where Level 1 is insufficient, and where thin liquids are confirmed to be aspirated. Key clinical risks are over-thickening, temperature-related drift, salivary amylase breakdown of starch thickeners, and reduced patient fluid intake. Xanthan gum thickeners offer greater consistency than starch-based products. All prescriptions should be documented with the full IDDSI term, verified by syringe test, and reviewed as clinical status changes.