ICD-10-CM code E83.42 is used to classify hypomagnesemia, a clinically significant disorder characterized by low magnesium levels in the blood. This code plays an important role in accurately documenting metabolic and electrolyte abnormalities that may influence patient management, clinical risk, and healthcare reporting.
Healthsure Hub created an article that serves as a coding-focused reference, explaining when and how E83.42 could be applied based on ICD-10-CM standards and documentation expectations.
What Is ICD-10-CM Code E83.42?
The official ICD-10-CM description of E83.42 is hypomagnesemia. In a clinical coding context, this code represents a provider-diagnosed condition in which laboratory testing confirms abnormally low serum magnesium levels that are considered clinically relevant.
The code is classified within:
- Endocrine, nutritional, and metabolic diseases (E00–E89)
- Disorders of mineral metabolism (E83)
Importantly, this type of code is a diagnostic code, not a symptom code. It should only be assigned when hypomagnesemia is clearly identified and documented by a qualified healthcare provider, rather than inferred from laboratory values alone.
Clinical Meaning of Hypomagnesemia in ICD-10 Coding
From a coding perspective, “low magnesium” refers to measurable reductions in serum magnesium levels identified through laboratory testing and interpreted by a provider as clinically meaningful. Magnesium plays a key role in neuromuscular function, cardiac conduction, and metabolic stability, which is why disturbances in magnesium balance are closely monitored in clinical care.
A critical distinction must be made between:
- Transient or incidental lab abnormalities, and
- Clinically documented hypomagnesemia that warrants diagnosis and monitoring.
This ICD-10-CM code is intended for the latter. Provider documentation is essential, as it establishes whether the abnormal laboratory finding rises to the level of a reportable diagnosis. Without explicit documentation, the code should not be assigned.
When Is ICD-10 Code Used?
The code is commonly reported in a range of healthcare settings, including:
- Hospital admissions
- Emergency department encounters
- Inpatient and outpatient metabolic or electrolyte evaluations
The code may be used as:
- A primary diagnosis when hypomagnesemia is the main reason for evaluation or treatment, or
- A secondary diagnosis when it affects clinical decision-making, monitoring, or overall care management.
Appropriate use of E83.42 typically involves laboratory-confirmed low magnesium levels accompanied by associated clinical significance, such as documented cardiac or neurological manifestations.
Examples may include arrhythmias or neurological issues that prompt further evaluation or intervention. However, the presence of symptoms alone does not justify coding unless the provider formally diagnoses hypomagnesemia.
Diagnostic Criteria Supporting The ICD-10 Code
Serum magnesium testing is the primary diagnostic tool used to identify hypomagnesemia. While reference ranges may vary slightly by laboratory, values below the established normal range prompt clinical consideration.
For ICD-10-CM coding purposes, assignment of the code requires more than an abnormal test result. The diagnosis should be supported by:
- Confirmed low serum magnesium levels, and
- Provider documentation linking the finding to clinical relevance, symptoms, or management decisions.
Abnormal laboratory values without interpretation or diagnosis by a provider do not meet the threshold for coding.
Common Causes Associated With E83.42
While the underlying cause is not required to assign the code, contextual documentation may support the diagnosis. Commonly associated factors include:
- Nutritional deficiencies
- Gastrointestinal losses
- Renal magnesium wasting
- Medication-related magnesium depletion
- Chronic medical conditions affecting mineral balance
These factors help explain why hypomagnesemia occurs but do not replace the need for a clearly documented diagnosis.
E83.42 vs. Related and Excluded ICD-10 Codes
The code should be carefully distinguished from other ICD-10-CM codes, including:
- Other electrolyte disorders, such as hypocalcemia or hypokalemia
- Nutritional deficiency codes when magnesium deficiency is classified differently
- Drug-induced or procedure-related conditions when separately reportable
Selecting the most accurate code requires attention to coding hierarchy, specificity, and provider documentation. Misclassification of electrolyte abnormalities can lead to inaccurate reporting and compliance risks.
Impact on Clinical Care and Billing
Accurate reporting of hypomagnesemia supports:
- Appropriate capture of clinical severity
- Risk adjustment and quality measurement initiatives
- Accurate reimbursement and claims processing
In inpatient settings, the code may contribute to documented complexity, while in longitudinal care it supports consistent tracking of metabolic abnormalities. At a broader level, correct coding improves the reliability of population health data and outcomes analysis.
Conclusion
ICD-10-CM code E83.42 represents clinically significant hypomagnesemia, not incidental laboratory findings. Correct use depends on laboratory confirmation combined with clear provider documentation of clinical relevance. For clinicians and coders alike, accurate application of this code supports compliant reporting, meaningful data capture, and high-quality healthcare documentation.
Used correctly, E83.42 serves as a reliable and authoritative diagnostic code within the ICD-10-CM classification system.
About the Author
