> ## 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 |


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