November 2012 Issue

Correcting Morning Blood Sugar Highs — Know the Causes of These Spikes and Ways to Treat Them
By Judith C. Thalheimer, RD, LDN
Today’s Dietitian
Vol. 14 No. 11 P. 18

Jill is frustrated. Her type 1 diabetes seems out of control, and she comes to your office at her wits’ end. She says she’s doing everything right: counting carbs, taking her insulin as prescribed, monitoring her blood glucose levels four times per day.

A look at Jill’s testing logs and most recent blood work confirms there’s a problem. She has a hemoglobin A1c of 9.2, and her blood glucose levels are all over the map. Her numbers generally are fine before she goes to bed but incredibly high in the morning. Recently, her physician increased her nighttime basal insulin dose to counteract the morning highs, but things seem worse now than ever. Her breakfast bolus doesn’t seem to be effective, and her high blood glucose levels persist into the afternoon.

“Fluctuating blood sugars can be very frustrating,” says Eileen M. Sturner, RD, LDN, CDE, BC-ADM. “RDs can play an important role in helping patients get to the bottom of problems such as morning highs. Working with patients to gather the appropriate data and facilitating the sharing of those data with the healthcare provider that’s managing their diabetes can have life-changing results.”

In type 1 diabetes, the pancreas can no longer provide either the steady drip of basal insulin that keeps blood sugar levels stable between meals or the bolus release of insulin that directs the uptake of glucose after eating. Patients must take basal insulin to keep their fasting blood sugar levels steady and bolus insulin to match their carbohydrate intake and correct highs.

The primary cause of hyperglycemia in type 1 diabetes is carbohydrate intake that isn’t matched with bolus insulin dosing. Perhaps Jill is underreporting her carbohydrate intake, administering her insulin incorrectly, or using expired insulin.

The morning highs caused Jill’s doctor to suspect that her basal insulin dose was too low to control her glucose levels overnight. While increasing the dose didn’t help in this case, too little basal insulin is a possible cause of hyperglycemia.
Stress on the body also can lead to hyperglycemia. Has Jill been injured or ill, or did she recently start an aggressive exercise regimen? If these scenarios are ruled out, the cause of her morning highs and lack of control may be, as she asserts, biological.

The Dawn Effect
In the dawn hours, many people experience a release of counterregulatory hormones. These hormones, such as human growth hormone (HGH), help with the growth, maintenance, and repair of our bodies while we sleep. They also make muscle tissue and the liver more resistant to the effects of insulin, meaning that more insulin is needed to maintain normal blood glucose levels. If there isn’t enough insulin to counteract the resistance, the result is morning hyperglycemia.

Carroll and Schade define the clinically relevant dawn effect as a dawn increase in blood glucose levels of more than 10 mg/dL or the increase in insulin requirements of at least 20% from the overnight nadir.1 By this definition, their review indicated that approximately 54% of patients with type 1 diabetes and 55% of patients with type 2 diabetes experience the dawn effect.1

Eating breakfast generally counteracts the effects of the early-morning hormones, returning blood sugar control to normal. For patients in whom the dawn effect is pronounced, a switch in nighttime basal insulin may be warranted. Taking the nighttime basal dose before bedtime instead of after dinner may help keep insulin levels from waning in the dawn hours. A switch from a long-acting basal insulin to one timed to peak in the early morning (such as NPH) may be considered. An insulin pump offers dosing flexibility that can respond to a patient’s specific increased morning insulin needs.

The Somogyi Effect
Another physiological cause of morning hyperglycemia is the Somogyi effect. Also known as rebound hyperglycemia or insulin-induced posthypoglycemic hyperglycemia, this phenomenon is named for the late Michael Somogyi, PhD, former professor of biochemistry at the Washington University and Jewish Hospital of St Louis, who first described it in a 1938 paper published in the Weekly Bulletin of the St. Louis Medical Society.

While the dawn effect occurs naturally in select individuals, the Somogyi effect is caused by administration of excessive insulin. Too much basal insulin before bed causes the patient’s blood sugar to drop overnight. If the blood sugar level reaches a dangerous low, the body reacts with an emergency release of counterregulatory hormones that increase glucose in the bloodstream. The patient is saved from a diabetic coma or death but awakens with hyperglycemia. The counterregulatory hormones continue to circulate in the body throughout the morning, causing insulin resistance that persists through breakfast and, in some patients, even through lunch. Perplexed patients find that their breakfast (and perhaps lunch) bolus fails to bring their blood sugar level down.

The Somogyi effect is an uncommon cause of morning hyperglycemia. As such, it’s easily overlooked. It’s counterintuitive to patients that too much insulin can cause hyperglycemia. Jill’s doctor logically raised her nighttime basal insulin dose in an attempt to correct her morning highs. Jill found that her highs didn’t improve and that her numbers remained high throughout the morning, despite attempts to correct them with bolus insulin.

Finding the Answers
So how can we help Jill and patients like her find the cause of their morning highs? The key is to track blood glucose levels overnight. If the nighttime and morning numbers are within 30 points of each other, the basal insulin dose is appropriate. A steady drop in blood glucose of more than 30 points indicates the dose is probably too high. A steady rise in blood glucose of more than 30 points indicates the dose is most likely too low. If blood glucose levels are stable overnight then rise significantly in the predawn hours, patients are experiencing the dawn effect. If blood sugar levels drop overnight to below 70 then rise abruptly, patients are experiencing the Somogyi effect and their nighttime basal insulin dose must be decreased.

To get the full picture of what’s happening overnight, patients should test their blood sugar levels before bed, at least twice during the night (2 AM and 4 AM work well), and in the morning before breakfast. Experts recommend choosing three nights for testing to ensure results are accurate. The nights need not be consecutive and should be on days the patient feels well, isn’t planning to exercise between dinner and bedtime, and has a blood sugar reading in the 100s four to six hours after dinner. A low-fat dinner is recommended; carbohydrate-rich snacks should be avoided between dinner and bedtime. Patients should present the test results to the doctor who’s managing their diabetes. They shouldn’t attempt to adjust their own basal insulin dosing.

“Nobody likes more finger sticks,” Sturner says, “and they certainly aren’t looking forward to getting up in the middle of the night to do it. It’s so important that we stress to patients the value of all this testing. Blood sugar numbers aren’t just something to report to their doctor. They’re tools to gain insight into what’s happening with their blood sugars. Testing is truly an essential component in their quest to gain control over their diabetes.”

Sturner also notes that continuous glucose monitoring, a recent advance in technology that allows around-the-clock blood sugar monitoring, is helping some patients avoid this burdensome, but potentially life-changing, sequence of tests.

— Judith C. Thalheimer, RD, LDN, is a freelance nutrition writer and community educator.


1. Carroll MF, Schade DS. The dawn phenomenon revisited: implications for diabetes therapy. Endocr Pract. 2005;11(1):55-64.