A rate-based quantity, such as 30 ml per hour, can be expressed as a **rateRatio** with coded numerator and denominator values. Where the unit of measure for the ratio is defined within UCUM (see Common UCUM Units), for example, “milliliter per hour”, it can also be expressed using the simpler **rateQuantity** structure.

## Dosage.rateRatio

Where the rate is expressed as coded numerator and denominator values.

## Dosage.rateQuantity

Where the unit of measure applicable to a rate is defined within UCUM which is mathematically equivalent to defining the rate using the more complex **rateRatio** structure.

## Dosage.rateRange

Where the unit of measure applicable to a rate range is defined within UCUM the **rateRange** structure can be used.