Found in Xcode by command clicking on one of the HKQuantityTypeIdentifiers in my code (eg HKQuantityTypeIdentifierBodyMassIndex). This is a list of all measurement types HealthKit can store and in the brackets on the end of each line is the iOS version it is available from.
/*--------------------------------*/
/* HKQuantityType Identifiers */
/*--------------------------------*/
// Body Measurements
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyMassIndex NS_AVAILABLE_IOS(8_0); // Scalar(Count), Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyFatPercentage NS_AVAILABLE_IOS(8_0); // Scalar(Percent, 0.0 - 1.0), Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierHeight NS_AVAILABLE_IOS(8_0); // Length, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyMass NS_AVAILABLE_IOS(8_0); // Mass, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierLeanBodyMass NS_AVAILABLE_IOS(8_0); // Mass, Discrete
// Fitness
HK_EXTERN NSString * const HKQuantityTypeIdentifierStepCount NS_AVAILABLE_IOS(8_0); // Scalar(Count), Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDistanceWalkingRunning NS_AVAILABLE_IOS(8_0); // Length, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDistanceCycling NS_AVAILABLE_IOS(8_0); // Length, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierBasalEnergyBurned NS_AVAILABLE_IOS(8_0); // Energy, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierActiveEnergyBurned NS_AVAILABLE_IOS(8_0); // Energy, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierFlightsClimbed NS_AVAILABLE_IOS(8_0); // Scalar(Count), Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierNikeFuel NS_AVAILABLE_IOS(8_0); // Scalar(Count), Cumulative
// Vitals
HK_EXTERN NSString * const HKQuantityTypeIdentifierHeartRate NS_AVAILABLE_IOS(8_0); // Scalar(Count)/Time, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyTemperature NS_AVAILABLE_IOS(8_0); // Temperature, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBasalBodyTemperature NS_AVAILABLE_IOS(9_0); // Basal Body Temperature, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBloodPressureSystolic NS_AVAILABLE_IOS(8_0); // Pressure, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBloodPressureDiastolic NS_AVAILABLE_IOS(8_0); // Pressure, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierRespiratoryRate NS_AVAILABLE_IOS(8_0); // Scalar(Count)/Time, Discrete
// Results
HK_EXTERN NSString * const HKQuantityTypeIdentifierOxygenSaturation NS_AVAILABLE_IOS(8_0); // Scalar (Percent, 0.0 - 1.0, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierPeripheralPerfusionIndex NS_AVAILABLE_IOS(8_0); // Scalar(Percent, 0.0 - 1.0), Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierBloodGlucose NS_AVAILABLE_IOS(8_0); // Mass/Volume, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierNumberOfTimesFallen NS_AVAILABLE_IOS(8_0); // Scalar(Count), Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierElectrodermalActivity NS_AVAILABLE_IOS(8_0); // Conductance, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierInhalerUsage NS_AVAILABLE_IOS(8_0); // Scalar(Count), Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierBloodAlcoholContent NS_AVAILABLE_IOS(8_0); // Scalar(Percent, 0.0 - 1.0), Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierForcedVitalCapacity NS_AVAILABLE_IOS(8_0); // Volume, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierForcedExpiratoryVolume1 NS_AVAILABLE_IOS(8_0); // Volume, Discrete
HK_EXTERN NSString * const HKQuantityTypeIdentifierPeakExpiratoryFlowRate NS_AVAILABLE_IOS(8_0); // Volume/Time, Discrete
// Nutrition
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFatTotal NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFatPolyunsaturated NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFatMonounsaturated NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFatSaturated NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryCholesterol NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietarySodium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryCarbohydrates NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFiber NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietarySugar NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryEnergyConsumed NS_AVAILABLE_IOS(8_0); // Energy, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryProtein NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminA NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminB6 NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminB12 NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminC NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminD NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminE NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryVitaminK NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryCalcium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryIron NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryThiamin NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryRiboflavin NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryNiacin NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryFolate NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryBiotin NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryPantothenicAcid NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryPhosphorus NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryIodine NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryMagnesium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryZinc NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietarySelenium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryCopper NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryManganese NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryChromium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryMolybdenum NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryChloride NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryPotassium NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryCaffeine NS_AVAILABLE_IOS(8_0); // Mass, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierDietaryWater NS_AVAILABLE_IOS(9_0); // Volume, Cumulative
HK_EXTERN NSString * const HKQuantityTypeIdentifierUVExposure NS_AVAILABLE_IOS(9_0); // Scalar (Count), Discrete
/*--------------------------------*/
/* HKCategoryType Identifiers */
/*--------------------------------*/
HK_EXTERN NSString * const HKCategoryTypeIdentifierSleepAnalysis NS_AVAILABLE_IOS(8_0); // HKCategoryValueSleepAnalysis
HK_EXTERN NSString * const HKCategoryTypeIdentifierSedentaryState NS_AVAILABLE_IOS(9_0); // HKCategoryValueSedentaryState
HK_EXTERN NSString * const HKCategoryTypeIdentifierCervicalMucusQuality NS_AVAILABLE_IOS(9_0); // HKCategoryValueCervicalMucusQuality
HK_EXTERN NSString * const HKCategoryTypeIdentifierOvulationTestResult NS_AVAILABLE_IOS(9_0); // HKCategoryValueOvulationTestResult
HK_EXTERN NSString * const HKCategoryTypeIdentifierMenstrualFlow NS_AVAILABLE_IOS(9_0); // HKCategoryValueMenstrualFlow
HK_EXTERN NSString * const HKCategoryTypeIdentifierVaginalSpotting NS_AVAILABLE_IOS(9_0); // HKCategoryValue
HK_EXTERN NSString * const HKCategoryTypeIdentifierSexualActivity NS_AVAILABLE_IOS(9_0); // HKCategoryValue
/*--------------------------------------*/
/* HKCharacteristicType Identifiers */
/*--------------------------------------*/
HK_EXTERN NSString * const HKCharacteristicTypeIdentifierBiologicalSex NS_AVAILABLE_IOS(8_0); // NSNumber (HKCharacteristicBiologicalSex)
HK_EXTERN NSString * const HKCharacteristicTypeIdentifierBloodType NS_AVAILABLE_IOS(8_0); // NSNumber (HKCharacteristicBloodType)
HK_EXTERN NSString * const HKCharacteristicTypeIdentifierDateOfBirth NS_AVAILABLE_IOS(8_0); // NSDate
HK_EXTERN NSString * const HKCharacteristicTypeIdentifierFitzpatrickSkinType NS_AVAILABLE_IOS(9_0); // HKFitzpatrickSkinType
/*-----------------------------------*/
/* HKCorrelationType Identifiers */
/*-----------------------------------*/
HK_EXTERN NSString * const HKCorrelationTypeIdentifierBloodPressure NS_AVAILABLE_IOS(8_0);
HK_EXTERN NSString * const HKCorrelationTypeIdentifierFood NS_AVAILABLE_IOS(8_0);
/*------------------------------*/
/* HKWorkoutType Identifier */
/*------------------------------*/
HK_EXTERN NSString * const HKWorkoutTypeIdentifier NS_AVAILABLE_IOS(8_0);