Type 1 Diabetes In Adults.

In November of 2013, endocrinologist Ira B. Hirsch stated that up to 25% of patients with Type I Diabetes will develop it in adulthood. (1)

What follows are from the Medscape Reference (2):

“The 2011 American Association of Clinical Endocrinologists (AACE) guidelines note that to help distinguish between the 2 types in children, physicians should measure insulin and C-peptide levels and immune markers (eg, glutamic acid decarboxylase [GAD] autoantibodies), as well as obtain a detailed family history.” 

“C-peptide is formed during conversion of proinsulin to insulin. An insulin or C-peptide level below 5 µU/mL (0.6 ng/mL) suggests type 1 DM; a fasting C-peptide level greater than 1 ng/dL in a patient who has had diabetes for more than 1-2 years is suggestive of type 2 (ie, residual beta-cell function). An exception is the individual with type 2 DM who presents with a very high glucose level (eg, >300 mg/dL) and a temporarily low insulin or C-peptide level but who will recover insulin production once normal glucose is restored.”

[However, Dr. Hirsch, in his lecture (1) said that in adults that the glutamic acid decarboxylase (GAD) antibodies are positive in only about 75% of type 1 patients and that measurement of C-peptide levels are of no help.]

Continuing the Medscape Reference (2):

“Ask about the type of insulin being used, delivery system (pump vs injections), dose, and frequency. Also ask about oral antidiabetic agents, if any. Of course, a full review of all medications and over-the-counter supplements being taken is crucial in the assessment of patients with type 1 DM.

“Patients using a pump or a multiple-injection regimen have a basal insulin (taken through the pump or with the injection of a long-acting insulin analogue) and a premeal rapid-acting insulin, the dose of which may be determined as a function of the carbohydrate count plus the correction (to adjust for how high the premeal glucose level is). In these patients, ask about the following:

  • Basal rates (eg, units per hour by pump, generally 0.4-1.5 U/h, potentially varying on the basis of time of day); the total daily dose as basal insulin is a helpful value to know
  • Carbohydrate ratio (ie, units of insulin per grams of carbohydrate, generally 1 unit of rapid-acting insulin per 10-15 g carbohydrate)
  • Correction dose (ie, how far the blood glucose level is expected to decrease per unit of rapid-acting insulin, often 1 U of insulin per 50-mg/dL decrease, though individuals with insulin resistance may need 1 U per 25-mg/dL decrease)
  • Some patients may be taking premeal pramlintide (an amylin analogue)”

The physician also needs to know the most recent Hemoglobin A1c and episodes of hypoglycemia (and what the symptoms were). He or she needs to review the (hopefully) computer record of blood sugars that the patient has recorded.

Audio-Digest Internal Medicine
Volume 61, Issue 13
April 7, 2014
Update on Diabetes – Irl B. Hirsch, MD
Update on Hyperlipidemia – Robert D. Brook, MD

(2) Type 1 Diabetes Mellitus Workup                                                                                               Medscape Reference, Updated: Jun 30, 2014 (Accessed 7-9-2014)

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