Hyperemesis Gravidarum ICD-10-CM codes

O21.0 is mild hyperemesis gravidarum starting before the end of the 20th week. O21.1 is hyperemesis gravidarum with metabolic disturbance such as dehydration, electrolyte imbalance, or carbohydrate depletion, and the index sends severe hyperemesis here as well. Because the metabolic disturbance is part of O21.1, do not separately report E86.0 (dehydration) or E87.1 (hyponatremia) alongside it; those codes belong with O21.0 or O21.9 only when the provider documents the disturbance without calling it hyperemesis.

O21.2 is late vomiting of pregnancy (excessive vomiting starting after 20 completed weeks). O21.8 is vomiting complicating pregnancy that is due to a disease classified elsewhere; code the underlying disease as well. O21.9 is vomiting of pregnancy, unspecified. Per the chapter 15 guidelines, nausea and vomiting in a pregnant patient are assumed to be pregnancy related unless the provider states otherwise, so R11.2 should not be used on a prenatal encounter without that statement.

Category O21 does not carry trimester characters. Add the Z3A weeks-of-gestation code to each encounter. Hyperemesis that persists into the second or third trimester keeps the O21 code that fits the documented onset and severity.