P71.2 vs R79.0
P71.2 and R79.0 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on R79.0
neonatal hypomagnesemia (P71.2)
P71.2
Neonatal hypomagnesemia
Billable
- Chapter 16
- Certain conditions originating in the perinatal period
- Section
- P70-P74
Indexed under
- Hypomagnesemia › neonatal
R79.0
Abnormal level of blood mineral
Billable
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R70-R79
Use when the record says
- Abnormal blood level of cobalt
- Abnormal blood level of copper
- Abnormal blood level of iron
- Abnormal blood level of magnesium
- Abnormal blood level of mineral NEC
- Abnormal blood level of zinc
Indexed under
- Abnormal, abnormality, abnormalities › blood level › cobalt
- Abnormal, abnormality, abnormalities › blood level › copper
- Abnormal, abnormality, abnormalities › blood level › iron
- Abnormal, abnormality, abnormalities › blood level › magnesium
- Abnormal, abnormality, abnormalities › blood level › mineral NEC
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027