Defining and identifying thickness of fluids and food for patients with swallowing difficulties

Karoline Brennan, Senior Medicines Information Pharmacist, North West Medicines Information CentrePublished

How fluid thickness and food texture are defined for patients with swallowing difficulties, and how to find the recommended level for a patient.


Many patients with dysphagia are unable to safely swallow thin liquids. Thin liquids can be aspirated (go down the wrong way), which can lead to pneumonia.

Thickened fluids can be swallowed more safely than thin liquids as they travel more slowly, allowing the person more time to co-ordinate the swallow response.

Defining thickness

IDDSI levels

Fluid consistency and food texture are graded according to the International Dysphagia Diet Standardisation Initiative (IDDSI) framework. This provides a common terminology and consists of a continuum of 8 levels ranging from 0 to 7. Drinks can be Levels 0 to 4, foods can be Levels 3 to 7:

  • IDDSI Level 0: ‘thin’ (the consistency of water)
  • IDDSI Level 1: ‘slightly thick’
  • IDDSI Level 2: ‘mildly thick’
  • IDDSI Level 3: ‘moderately thick’ (the same consistency as liquidised food)
  • IDDSI Level 4: ‘extremely thick’ (the same consistency as pureed food)

Thickening agents can be used to modify the consistency of thin liquids to IDDSI Levels 1, 2, 3 or 4.

Finding the correct thickness level for the patient

The speech and language therapist will determine the appropriate IDDSI Levels of fluid consistency and food texture for the patient. This will be documented in the swallow assessment report.

It is important to find out the consistency of fluid and food a person can swallow safely. Too thin and the patient is at risk of aspiration, too thick and the liquid can leave a residue that can be aspirated.

Specific advice

Using thickeners of different types for patients with swallowing difficulties

Gum and starch based thickeners are available; drug-thickener interactions are possible and should be avoided.

Thickening liquid medicines

Thickening liquid medicines should not be used routinely: it is difficult to check fluid consistency which can affect whether the medicine is swallowed safely.

Storage and regulation of thickeners and thickened fluids

Thickeners and thickened fluids have different storage requirements and are regulated in a particular manner.

Read more

Swallowing difficulties

All our advice on using medicines safely and effectively in patients with swallowing difficulties