ICD-10-CM Coding for Magnesium Screening
Use ICD-10-CM code Z13.228 (Encounter for screening for other metabolic disorders) for routine screening checks of serum magnesium in asymptomatic patients.
Primary Coding Options
For a straightforward screening magnesium check without symptoms or known deficiency, Z13.228 is the most appropriate code as it specifically covers screening for metabolic disorders including electrolyte screening. 1, 2
If the patient has documented hypomagnesemia (serum magnesium <0.85 mmol/L or <2.07 mg/dL), use E83.42 (Hypomagnesemia) instead of a screening code. 3
Clinical Context Determines Code Selection
When to Use Symptom-Based Codes Instead
If checking magnesium due to specific clinical presentations, code the presenting symptom rather than screening:
- R25.2 (Cramp and spasm) – for muscle cramps or tetany 4
- R42 (Dizziness and giddiness) – for neurological symptoms 5
- R53.83 (Other fatigue) – for unexplained fatigue 4
- I49.9 (Cardiac arrhythmia, unspecified) – if checking due to arrhythmia risk 6, 4
When to Use Condition-Specific Codes
If the magnesium check is part of monitoring a known condition, code the underlying condition as primary:
- K91.2 (Postsurgical malabsorption, not elsewhere classified) – for short bowel syndrome patients 6, 4
- K90.9 (Intestinal malabsorption, unspecified) – for malabsorption disorders 4
- N18.3-N18.6 (Chronic kidney disease, stage 3-5) – for renal patients on dialysis 4
- Z79.899 (Other long term drug therapy) – for patients on magnesium-wasting medications (diuretics, PPIs, calcineurin inhibitors) 4, 7
Common Clinical Scenarios
For patients on chronic diuretic therapy requiring routine magnesium monitoring, use Z79.4 (Long term use of insulin) as secondary with the primary cardiac condition (e.g., I50.9 for heart failure), then check magnesium as part of that management. 7
For patients with documented risk factors (chronic diarrhea, high-output stoma, chemotherapy), code the specific risk factor rather than using a screening code. 6, 5
Critical Coding Pitfalls
Never use a screening code (Z13.228) if the patient has known hypomagnesemia or symptoms – this will result in claim denial. Use E83.42 or the symptom code instead. 1, 2
Avoid using "abnormal findings" codes (R79.0) for initial testing – these are for follow-up of previously abnormal results, not initial screening. 2
Do not code hypermagnesemia (E83.41) unless serum magnesium is >2.2 mEq/L with clinical manifestations, as this represents a different clinical entity requiring different management. 6
Documentation Requirements
To support the screening code Z13.228, documentation should indicate:
- Patient is asymptomatic for magnesium deficiency
- Test is being performed for preventive/screening purposes
- Patient has risk factors warranting screening (medication use, malabsorption, renal disease) 4, 7
If any symptoms are present or there is known deficiency, the screening code becomes inappropriate and a diagnostic code must be used instead. 1, 2