Codes under category 249, Secondary diabetes mellitus, identify complications/manifestations associated with secondary diabetes mellitus.
Secondary diabetes is always caused by another condition or event (e.g., cystic fibrosis, malignant neoplasm of pancreas, pancreatectomy, adverse effect of drug, or poisoning).
a. Fifth-digits for category 249:
A fifth-digit is required for all category 249 codes to identify whether the diabetes is controlled or uncontrolled.
b. Secondary diabetes mellitus and the use of insulin
For patients who routinely use insulin, code V58.67, Long-term (current) use of insulin, should also be assigned. Code V58.67 should not be assigned if insulin is given temporarily to bring a patient’s blood sugar under control during an encounter.
c. Assigning and sequencing secondary diabetes codes and associated conditions When assigning codes for secondary diabetes and its associated conditions (e.g. renal manifestations), the code(s) from category 249 must
be sequenced before the codes for the associated conditions. The secondary diabetes codes and the diabetic manifestation codes that correspond to them are paired codes that follow the etiology/manifestation convention of the classification. Assign as many codes from category 249 as needed to identify all of the associated conditions that the patient has. The corresponding codes for the associated conditions are listed under each of the secondary diabetes codes. For example, secondary diabetes with diabetic nephrosis is assigned to
code 249.40, followed by 581.81.
 
d. Assigning and sequencing secondary diabetes codes and its causes
The sequencing of the secondary diabetes codes in relationship to codes for the cause of the diabetes is based on the reason for the encounter, applicable ICD-9-CM sequencing conventions, and chapter-specific guidelines.
If a patient is seen for treatment of the secondary diabetes or one of its associated conditions, a code from category 249 is sequenced as the principal or first-listed diagnosis, with the cause of the secondary diabetes (e.g. cystic fibrosis) sequenced as an additional diagnosis.
If, however, the patient is seen for the treatment of the condition causing the secondary diabetes (e.g., malignant neoplasm of pancreas), the code for the cause of the secondary diabetes should be sequenced as the principal or first-listed diagnosis followed by a code from category 249.
 
i. Secondary diabetes mellitus due to pancreatectomy
For postpancreatectomy diabetes mellitus (lack of insulin due to the surgical removal of all or part of the pancreas), assign code 251.3, Postsurgical hypoinsulinemia. A code from subcategory 249 should not be assigned for secondary diabetes mellitus due to pancreatectomy. Code also any diabetic manifestations (e.g. diabetic nephrosis 581.81).
 
ii. Secondary diabetes due to drugs
Secondary diabetes may be caused by an adverse effect of correctly administered medications, poisoning or late effect of poisoning.