What Is IDDSI Level 1: Slightly Thick?

IDDSI Level 1 is the first step up from normal thin liquids. Known as Slightly Thick, it was previously described using the term “nectar consistency” in older dysphagia frameworks — though IDDSI has moved away from food-named descriptors to avoid ambiguity. Level 1 liquids flow faster than syrup but noticeably slower than water, with a slight resistance that gives the swallowing mechanism a fraction more time to respond safely.

Syringe flow test result: 1–4ml remaining in a 10ml syringe after 10 seconds. This means most of the liquid has flowed out, but measurably more remains compared to Level 0.

Who Is Level 1 Prescribed For?

Level 1 is typically prescribed for patients who can manage somewhat faster-flowing liquids but where thin water creates aspiration risk. It is commonly seen in:

• Mild post-stroke dysphagia — where the delay in swallowing reflex is minimal
• Early Parkinson’s disease — where some thickening provides a useful safety margin without significantly impacting quality of life
• Mild neurological dysphagia — where the swallowing mechanism is slightly slowed but not severely impaired
• Transition phases — patients stepping down from Level 2 as swallowing function improves

A speech therapist determines the appropriate level through clinical assessment — caregivers should not select the level independently.

The IDDSI Flow Test for Level 1

To verify that a prepared liquid meets Level 1 criteria:

1. Fill a clean 10ml syringe with the liquid to be tested
2. Hold the syringe tip downward, finger covering the outlet
3. Simultaneously release your finger and start a 10-second timer
4. At exactly 10 seconds, cover the outlet again
5. Read the residual volume in the syringe

Result: 1–4ml remaining = Level 1 (Slightly Thick)

If less than 1ml remains, the liquid is Level 0 (too thin). If more than 4ml remains, the liquid is Level 2 or thicker. Adjust thickener quantity and re-test.

Commercial Thickeners Available in Hong Kong

Several thickener products are available through Hong Kong pharmacies, medical supply stores, and specialist suppliers. They fall into two main categories:

Starch-Based Thickeners

Starch-based thickeners (typically made from modified corn starch or tapioca starch) are generally less expensive and widely available.

Characteristics:

• Continue to thicken over time as the liquid cools or sits
• Flavour and appearance may become cloudy
• Less predictable consistency if preparation time varies
• Lower cost — suitable for high-volume use in care homes

Examples available in HK: Various pharmacy-brand thickening powders, some institutional supply products.

Xanthan Gum-Based Thickeners

Xanthan gum thickeners are generally considered the higher-quality option for clinical use.

Characteristics:

• More stable over time — consistency does not change significantly as temperature changes
• Clear appearance — does not cloud liquids
• Works with most beverages including acidic juices
• Higher cost — typically used for home care or smaller volume settings

Brands available in Hong Kong:

• Resource ThickenUp Clear (Nestlé Health Science) — xanthan gum, widely available at Watson’s, Mannings, and larger pharmacies
• Nutilis Clear (Nutricia) — xanthan gum, available through medical supply and some pharmacies
• Thick & Easy Clear — available through specialist medical suppliers
• QUIK-THIK and similar institutional products — available through hospital and RCHE supply chains

Important: Different brands may require different quantities to achieve the same IDDSI level. Always verify with the syringe flow test after switching brands. Do not assume equivalence between products.

Preparing Level 1 Liquids: Practical Guidance

General Preparation Tips

• Stir thoroughly — undissolved thickener creates lumps and inconsistent texture
• Follow the brand’s instructions as a starting point, then verify with the flow test
• Note water temperature — hot liquids often require more thickener to reach the same consistency as room-temperature liquids (especially with starch-based products)
• Allow standing time — some products continue to thicken for 1–2 minutes after mixing

Common Liquids in Hong Kong Context

Creating a Preparation Record

For consistency across care shifts, create a written standard for each commonly served drink:

Storage and Safety

• Prepare thickened liquids fresh before each serving when possible
• If pre-preparing (e.g. for overnight in a care home), store in a covered, labelled container in the refrigerator
• Re-test consistency before serving if prepared more than 2 hours in advance — starch-based thickeners in particular continue to thicken in the refrigerator
• Never add more thickener to a liquid that is already close to the correct level without re-testing — over-thickening is a common error that creates Level 2 or 3 when Level 1 is required

Patient Experience Considerations

Many patients prescribed Level 1 find the slightly altered mouthfeel noticeable but acceptable, particularly when using xanthan gum-based products which are nearly tasteless and clear. Common patient concerns include:

• “It doesn’t taste the same” — select a clear, flavour-neutral thickener
• “I don’t want to drink more than I have to” — hydration monitoring is important; some patients reduce fluid intake when drinks are thickened
• “The texture is lumpy” — ensure thorough stirring and sufficient standing time; consider a xanthan gum product for smoother results

Maintaining adequate hydration is a significant concern in dysphagia management. For guidance, see Hydration and Thickened Fluids.

Related Resources

• IDDSI Level 0: Thin Liquids
• IDDSI Testing at Home
• Thickener Comparison Guide for Hong Kong
• Choosing a Thickener

Information on this page is for educational purposes only and does not constitute medical advice. IDDSI dietary levels must be determined by a speech therapist following individual assessment.