> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metriport.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SubstanceAmount

> Base StructureDefinition for SubstanceAmount Type: Chemical substances are a single substance type whose primary defining element is the molecular structure. Chemical substances shall be defined on the basis of their complete covalent molecular structure; the presence of a salt (counter-ion) and/or solvates (water, alcohols) is also captured. Purity, grade, physical form or particle size are not taken into account in the definition of a chemical substance or in the assignment of a Substance ID.

## Properties

| Name              | Required | Type                                                                                                   | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| ----------------- | -------- | ------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| id                | No       | string                                                                                                 | Unique id for inter-element referencing                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| extension         | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                 | Additional content defined by implementations                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| modifierExtension | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                 | Extensions that cannot be ignored even if unrecognized                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| amount\[x]        | No       | [Quantity](/medical-api/fhir/data-types/quantity), [Range](/medical-api/fhir/data-types/range), string | Used to capture quantitative values for a variety of elements. If only limits are given, the arithmetic mean would be the average. If only a single definite value for a given element is given, it would be captured in this field                                                                                                                                                                                                                                                               |
| amountType        | No       | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept)                                        | Most elements that require a quantitative value will also have a field called amount type. Amount type should always be specified because the actual value of the amount is often dependent on it. EXAMPLE: In capturing the actual relative amounts of substances or molecular fragments it is essential to indicate whether the amount refers to a mole ratio or weight ratio. For any given element an effort should be made to use same the amount type for all related definitional elements |
| amountText        | No       | string                                                                                                 | A textual comment on a numeric value                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| referenceRange    | No       | Element                                                                                                | Reference range of possible or expected values                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| - id              | No       | string                                                                                                 | Unique id for inter-element referencing                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| - extension       | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                 | Additional content defined by implementations                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| - lowLimit        | No       | [Quantity](/medical-api/fhir/data-types/quantity)                                                      | Lower limit possible or expected                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| - highLimit       | No       | [Quantity](/medical-api/fhir/data-types/quantity)                                                      | Upper limit possible or expected                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |