Subcutaneous insulin is not an absolute contraindication in dengue with platelets 23,000/µL. If insulin is medically needed, particularly for type 1 diabetes, marked hyperglycemia, or ketosis, it generally should not be stopped solely because platelets are low.

However, at 23k and falling, the patient is in a high-risk dengue period and should be managed in hospital or under urgent clinician supervision:

The greater concern is the dengue itself: a rapidly declining platelet count, especially around defervescence, can signal the critical phase, and diabetes is an associated risk factor that warrants closer observation. PAHO includes diabetes among conditions for which dengue patients need closer assessment/observation in its clinical-management algorithms.

Seek urgent emergency assessment now if there is any bleeding, black stools/vomiting blood, severe abdominal pain, repeated vomiting, drowsiness/restlessness, cold clammy extremities, breathing difficulty, little urine, dizziness/fainting, or rising hematocrit with falling platelets.

If you mean insulin for a specific glucose value, the safest choice depends on whether the person has type 1 or type 2 diabetes, their current glucose, oral intake, hydration, kidney function, and whether ketones are present.