Cases illustrating intensive insulin therapy in special situations

INTRODUCTION — Adults with diabetes who are motivated and well educated can often keep their blood glucose concentrations in the target or near-target range on routine days. They may, however, need advice for more unusual events. Although it is not possible to cover all eventualities, some management guidelines can be given for special situations.

Glycemic control in general is reviewed in separate topics:

●(See "Initial management of hyperglycemia in adults with type 2 diabetes mellitus".)

●(See "Management of persistent hyperglycemia in type 2 diabetes mellitus".)

●(See "Management of blood glucose in adults with type 1 diabetes mellitus".)

EATING OUT — Maintenance of glycemic control with intensive insulin therapy is facilitated by use of an insulin-to-carbohydrate ratio or by relative consistency in the quantity and timing of carbohydrate intake. However, the amount of carbohydrate to be consumed may be difficult to anticipate when going to a restaurant or eating at a friend's house. In addition, high fat/protein meals may also increase the magnitude and duration of hyperglycemia after the meal. Blood glucose responses to mixed meals high in protein and/or fat along with carbohydrate have been found to differ among individuals.

The person with diabetes should try to estimate (visually or by asking the chef) the carbohydrate content in the meal. If not using continuous glucose monitoring, it is helpful to check their blood glucose before the meal, two hours after the meal, and if symptoms of hypo- or hyperglycemia occur. It is also important to keep a carbohydrate supply on hand in case the meal is delayed and unexpected hypoglycemia develops.

The use of insulin pens and rapid-acting analogs (such as insulin lispro, insulin aspart, or insulin glulisine) have made eating out more convenient and have reduced the danger of hypoglycemia four to eight hours after the injection (compared with regular insulin).

Case 1 — A 41-year-old man, whose type 1 diabetes is usually well controlled (glycated hemoglobin [A1C] of 6.9 percent), takes:

●Before breakfast – 6 to 10 units of insulin aspart and 28 units of insulin degludec

●Before lunch – 4 to 8 units of insulin aspart

●Before evening meal – 6 to 12 units of insulin aspart

One evening, after a busy day at work, he is invited to dinner with friends. Dinner will not be served until approximately 8:30 PM, although he usually eats his evening meal at approximately 5:45 PM. His blood glucose values for that day were:

●Before breakfast, 106 mg/dL (5.9 mmol/L)

●Before lunch, 112 mg/dL (6.2 mmol/L)

●At 5:30 PM, 68 mg/dL (3.8 mmol/L)

Because of the relatively low blood glucose value at 5:30 PM, he eats a 15-gram carbohydrate snack. At 8:15 PM, after arriving at the dinner party, his blood glucose is 137 mg/dL (7.6 mmol/L). This seems to be a reasonable value, and he decides to take 8 units of insulin aspart before the evening meal. When he gets home at 11 PM, having eaten more than usual, his blood glucose is 362 mg/dL (20.1 mmol/L). He wonders what to do now.

Interpretation — To correct the hyperglycemia, he could take a conservative extra (correction) bedtime dose of insulin aspart (2 to 3 units), keeping in mind that the supplemental insulin will be having its effect in the middle of the night when he is asleep and as the glycemic effects of the meal are dissipating. It is important not to try to catch up with hyperglycemia in one step. Correction doses, especially at bedtime, should not be selected to achieve normoglycemia by the next morning; rather, enough insulin should be given to lower the morning blood glucose level and then further adjustments of the morning dose can get the glucose to the desired range thereafter.

To prevent the bedtime hyperglycemia, he should have taken more than his usual dose of aspart insulin before the meal, or eaten less. Depending upon how well he knew the hosts, he might have asked what was going to be served so that he could have made a better guess as to the appropriate insulin dose. If the patient is taught detailed carbohydrate counting, including insulin-to-carbohydrate ratios, his ability to estimate how much extra rapid-acting insulin to take would improve. It would also be helpful to teach him to use a correction (insulin sensitivity) factor. (See "Nutritional considerations in type 1 diabetes mellitus", section on 'Insulin dosing'.)

During consumption of the meal or immediately after eating, when the patient realized he was eating or ate more carbohydrate than normal, he could have immediately taken supplemental rapid-acting insulin to cover the additional amount of carbohydrate, thereby avoiding or reducing bedtime hyperglycemia. If one to two hours have passed since the meal was completed and the individual wants to take extra insulin to cover additional carbohydrates consumed, he should administer only 50 to 60 percent of the calculated dose. However, if one to two hours since the meal is close to bedtime, a smaller dose (eg, 30 to 40 percent of the calculated dose) can be administered.

ELECTIVE MINOR SURGERY — Some minor surgery is performed in the fasting state. This is a potential problem for people receiving intensive insulin therapy in whom fasting could predispose to intraoperative hypoglycemia.

Case 2 — A 52-year-old man with type 1 diabetes of four years duration requires elective oral surgery for extraction of some teeth at 8 AM the next day. He has been told to come in fasting, and the procedure will be done under local anesthesia. His usual insulin regimen is 32 units of insulin glargine in the morning and a variable dose of lispro based on his carbohydrate intake (1 unit for every 8 grams of carbohydrate plus a correction factor of 1 unit for every 30 mg/dL that his pre-meal blood glucose is above his target glucose of 120 mg/dL). His fasting blood glucose average for the past 14 days has been 138 mg/dL (range 94 to 178 mg/dL [5.2 to 9.9 mmol/L]). He asks for advice on how to prepare for surgery.

●The simplest approach is to advise him to reduce the dose of insulin glargine on the morning of surgery by approximately 20 percent (ie, take approximately 25 units).

●Alternatively, to determine a safe dose of insulin glargine for the morning of surgery, several days prior to surgery he can be instructed to take his usual morning dose of 32 units of insulin glargine and postpone eating breakfast and the usual breakfast lispro administration until late morning. If his glucose readings remain stable, it is safe for him to take his usual dose of 32 units of glargine on the morning of surgery. However, if the glucose readings fall during the morning, the dose of insulin glargine should be reduced by 20 percent to 25 units (approximately 80 percent of the usual dose) on the morning of surgery.

●He should not take lispro when fasting on the morning of surgery.

After the procedure is over and he feels well enough to eat (which is likely to be liquids or soft food later that same morning), he should check his glucose, take the remainder of his usual morning insulin glargine dose (7 units) if he took the reduced dose that morning, and use his usual calculations to cover his lunch based on the amount of carbohydrate he is about to consume and his pre-meal blood glucose reading. (See "Perioperative management of blood glucose in adults with diabetes mellitus", section on 'Type 1 or insulin-treated type 2 diabetes'.)

Although he has been told to fast, he should carry fast-acting carbohydrate (such as glucose tablets) with him in case his blood glucose drops into or near hypoglycemic range.

IMPENDING OR MILD-MODERATE DIABETIC KETOACIDOSIS — Mild infections (such as a cold, sore throat, or urinary tract infection) can, via the release of stress hormones, cause persistent hyperglycemia and some ketonuria. The clinician can often manage this problem over the telephone if the person with diabetes is reliable and well educated, with frequent monitoring of blood glucose and urine ketones.

Case 3 — A 24-year-old woman, who has had type 1 diabetes for nine years, has sudden deterioration of her glucose control in association with an intercurrent flu-like illness. Her usual regimen is:

●Before breakfast – 6 units of insulin aspart and 12 units of insulin glargine

●Before the evening meal – 6 units of aspart

●Bedtime – 10 units of glargine

She awakens with a blood glucose value of 475 mg/dL (26.4 mmol/L) and moderate ketones in the urine. She has some myalgias, a slight cough, and a temperature of 99.6°F. She does not feel hungry but is not nauseated. She decides to stay home from work. Over the telephone, the diabetes nurse specialist tells her to take her usual morning dose of 12 units of glargine plus an extra 8 units of insulin aspart (14 units in all) and to drink at least two to three cups of water or diet soft drink every hour.

She checks her blood glucose and tests her urine for ketones every hour; she also contacts a member of the diabetes team every one to two hours. She is told that, even though her blood glucose is high, she should take in some carbohydrate (perhaps 150 grams) during the day. This can be achieved by drinking fruit juice in addition to sipping plain water or diet soft drinks. However, her blood glucose remains above 300 mg/dL (16.7 mmol/L), and three hours later, she develops large ketonuria and is unable to maintain her fluid intake because of uncontrolled nausea and vomiting. As a result, prompt arrangements are made for her to come to the emergency department. (See "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Clinical features, evaluation, and diagnosis" and "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Treatment".)

Interpretation — Although ultimately unsuccessful in this case, it is often possible to manage mild or moderate diabetic ketoacidosis (DKA) with the individual at home and calling in frequently. Reasonable general guidelines are as follows:

●For moderate to large ketonuria (or blood ketones >1 mmol/L), give approximately 20 percent of the total daily dose of insulin (20 percent of 34 units = approximately 7 units) as regular or rapid-acting insulin

●For trace-mild ketonuria (or blood ketones <0.6 mmol /L), give a correction dose based on the insulin sensitivity (correction) factor or 10 percent of the total daily dose (whichever calculated dose is higher)

If there is improvement after two to three hours, give supplemental rapid-acting insulin (the dose is typically based on the individual sensitivity [correction] factor) every two to four hours (or regular insulin every four to six hours) in addition to the person's usual insulin regimen until the glucose reading is <250 mg/dL (13.9 mmol/L) with negative to small urine ketones.

This approach can be used with reliable, motivated individuals, who are able to maintain an adequate fluid intake. An anti-emetic may be helpful in people with nausea and vomiting. If oral intake is inadequate, or if there are concerns about the patient's reliability or functional status, they should be brought to the emergency department or doctor's office for intravenous fluid replacement and further evaluation and management.

Case 4 — A 42-year-old man has had type 1 diabetes for 20 years and has been successfully using a continuous subcutaneous insulin infusion (CSII) device (insulin pump) for the past five years with insulin aspart (most recent glycated hemoglobin [A1C] is 6.4 percent with very few hypoglycemic episodes). His basal rate is 1.1 units per hour from 2 to 10 AM and 0.9 units per hour from 10 AM to 2 AM. His usual pre-meal bolus is 1 unit for every 10 grams of carbohydrate at breakfast and lunch and 1 unit for every 15 grams of carbohydrate before his evening meal. At all three meals, his correction factor is 1 unit for every 30 mg/dL that his pre-meal blood glucose is above 120 mg/dL.

After a stressful day at work, he goes to bed at 9 PM. He awakes at 5 AM the next morning after a fitful sleep feeling thirsty, with a headache, and bursting to urinate. He realizes that sometime during the night, his pump catheter has become dislodged and is lying loose in the bedclothes. His blood glucose is 494 mg/dL. Although tired and slightly nauseous, he is alert and is able to drink three large glasses of water and keep them down. He has moderate urine ketones. He calls his diabetes care team to ask advice on what to do. He is given the following instructions:

●Prepare a fresh insulin infusion set and insert it in a new location on his abdomen. He should set the basal rate at 1.1 units per hour and give himself a bolus of insulin aspart equivalent to 20 percent of his total daily dose (eg, 20 percent of 50 units = 10 units of aspart) right away.

●Drink at least two large glasses of water every hour and check his blood glucose every hour and to call back in three hours.

At 8 AM, his blood glucose is down to 346 mg/dL and he has only trace ketones in his urine. He takes another bolus of 7.5 units of aspart (based on his insulin sensitivity or correction factor) and continues to drink water and check his blood glucose hourly. By 11 AM, his blood glucose is 197 mg/dL (10.9 mmol/L) with a trace of ketonuria. His headache is gone, and he feels well enough to eat something. He is told to reduce his basal rate back to 0.9 units per hour and to use his usual formula to calculate his lunchtime bolus. He has a large bowl of soup and two pieces of bread for a total of 60 grams of carbohydrate, so he takes a total of 9 units of aspart to cover this. His next glucose readings (at 2 PM) is 164 mg/dL (9.1 mmol/L), and his ketonuria has resolved. By that evening he feels back to normal.

Interpretation — CSII is a very effective and flexible way for motivated individuals with type 1 diabetes to achieve excellent glycemic control as they take no long-acting insulin (relying instead on a continuous infusion of rapid-acting insulin). However, they are at risk of developing DKA quickly if the flow of rapid-acting insulin is interrupted. When the catheter gets dislodged, the plasma insulin level will quickly fall, resulting in the development of hyperglycemia and ketosis.

Individuals using CSII should have some long-acting insulin (such as glargine or detemir) on hand to use if their pump has a major malfunction. In a case like this one, however, where the pump is functioning correctly but the catheter became dislodged, and where the person does not have an intercurrent illness and is alert and feeling well enough to keep fluids down, the situation can be managed at home using an approach like the one described here. (See "Continuous subcutaneous insulin infusion (insulin pump)", section on 'Safety considerations'.)

If there is any concern regarding whether the pump is functioning correctly, the initial bolus of insulin aspart should be given by injection using a syringe or insulin pen. When there is pump malfunction, the pump should be disconnected and both basal insulin, such as glargine, and rapid-acting insulin should be given by injection with a syringe or pen.

●The long-acting insulin dose is based upon the basal insulin dose delivered by the pump, either the full 24-hour basal insulin dose (23 units), or the lowest hourly infusion rate (0.9 units/hour x 24 hours = approximately 22 units).

It should be given as either a single injection of long-acting insulin or half the dose every 12 hours.

●The rapid-acting insulin should be given as described above (see 'Case 3' above), until blood glucose levels are in the 200 to 250 mg/dL (11.1 to 13.9 mmol/L) range, and urine ketones have mostly or completely cleared. (See "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Clinical features, evaluation, and diagnosis" and "Diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults: Treatment".)

ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge David McCulloch, MD, who contributed to earlier versions of this topic review.