Timing insulin, the last installment

Never mind what you call that!!! How high am I going to go?!


 The American Diabetes Association advises that postprandial blood glucose shouldn’t exceed 180 mg/dl (plasma value) at two hours after the start of a meal. Personally I find this number exceedingly high and was surprised it was not lowered in their recent January 2009 Standards of Care. Many other diabetes educators I know find it high as well and several other associations and experts believe the two-hour postmeal goal should be less than 140 mg/dl. Whew! Better. 

I’ve placed two posts here in the last two weeks that are excerpts from Hope Warshaw’s (R.D., B.C.-A.D.M., C.D.E.) wonderful article, “Rapid-Acting Insulin
Timing It Just Right.” Diabetes educator and dietitican Warshaw explains how to better time your insulin with your meals to get your post prandial blood sugars where you want them. Among the suggestions are occasionally checking your blood glucose after a meal at hours one, two, and three to help you determine when your blood glucose level peaks and starts to come down again. The overall key to controlling postprandial highs is better timing of rapid-acting insulin. Here are several other useful tips from her article:  

Low glycemic index foods – If your blood glucose is less than 100 mg/dl before a meal and you plan to have a meal with a low glycemic index, wait until you start to eat to take your rapid-acting insulin.

Uncertain carbohydrate intake – If you don’t know how much carbohydrate you will eat at a meal, consider splitting your rapid-acting insulin dose. Take enough insulin before the meal to cover the amount of carbohydrate you are sure you will eat. Then as the meal goes on and you know how much more carbohydrate you will eat, take more insulin to cover that amount. This method is easiest if you are on an insulin pump. (But I can attest that it’s doable even on Multiple Daily Injections)

Drawn-out meals – Pump users who are planning to have a meal that is eaten over time, such as a cocktail party or Thanksgiving dinner or a meal that is higher in fat or lower in glycemic index and high in fiber, (it will slow your glucose rise) may use one of the optional bolus delivery tools on their insulin pump. Most insulin pumps allow you to deliver a bolus over time rather than all at once or to deliver some of the bolus immediately and the rest over the next few hours. People who inject insulin could take half their bolus at the start of a meal and the other half an hour or two later. (I do this and sometimes even inject 3 x as I graze. No it’s not fun but it does help more closely match the correct dose of insulin to what and when you’re actually eating.)

Snacks – Alison Evert, R.D., C.D.E., a diabetes educator at Joslin Diabetes Center at Swedish Hospital in Seattle, advises people to “take rapid-acting insulin with any amount of carbohydrate over 10 grams.” Although it is common to think that a few grams won’t make a big difference, the reality is that 10 grams of carbohydrate can raise many peoples’ blood glucose 30 or more points.

Unused bolus insulin – While the duration of action of rapid-acting insulin is usually given as 3–4 hours, some diabetes experts believe it may continue to lower blood glucose level for as long as 5 hours. You can assume that about 20% of a dose of rapid-acting insulin is used each hour after it is given. In John Walsh’s book Using Insulin and on his Web sitehttp://diabetesnet.com/diabetes_control_tips/bolus_on_board.php, he provides a table that shows insulin activity at 1, 2, 3, 4, and 5 hours after bolus doses of insulin from 1 to 10 units.

When two doses of rapid-acting insulin overlap, their effects overlap, too, and the result can be hypoglycemia. Therefore, when you’re considering the size of a bolus dose of insulin, it is critical that you factor in what Walsh calls “the unused insulin” or “bolus [insulin] on board.” This is the amount of “active” rapid-acting insulin left from a previous injection or bolus dose from a pump that continues to lower your blood glucose.

For instance, before lunch, you take a bolus of rapid-acting insulin. Three hours later you decide to have a snack with 30 grams of carbohydrate. You check your blood glucose and find that it’s high at 195 mg/dl. Assuming 1 unit of insulin for you covers  45 mg/dl, you calculate you’ll need two units of insulin to bring your blood glucose level down to your premeal target of 100 mg/dl and another two units to cover the snack you’re about to eat. You take the insulin, and several hours later, your blood glucose has dropped to 55 mg/dl. Why? Because you didn’t factor in the hour or so of action left from the bolus or injection you took at lunch.

To prevent hypoglycemia from unused insulin, get in the habit of thinking about when you took your last bolus dose and how much (if any) action is still left before taking another bolus to “correct” high blood glucose. Most pumps have a built-in feature that keeps track of how much of a previous bolus dose is still active. For us MDI people we have to log it on paper or in our heads.

Even though I’ve had diabetes for 37 years and injected insulin for 32 (Yes, I’m a type 1 who was misdiagnosed with type 2 and on oral meds the first 5 years) you can always learn something new or refresh what you know. 

Thank you Hope. 

More tips for timing insulin

A few posts ago I extracted some very valuable information from an article CDE and dietitian, Hope Warshaw wrote titled, “Rapid-Acting Insulin, Timing It Just Right” and I’d like to share a little more of her knowledge.

 Fine-tuning the timing of your premeal boluses or injections is important, but no more so than knowing how to count the carbohydrates in a meal or snack. If you don’t know how to count carbohydrates or to match your insulin dose to the amount of carbohydrate you plan to eat, speak to your health-care provider. Many people find themselves in a reactive mode when it comes to dosing insulin, taking it in response to high blood glucose rather than using enough of it before a meal to cover the rise of blood glucose in the hours after a meal or snack. Experts agree that it’s much harder to bring high blood glucose back down than to control blood glucose levels with sufficient insulin in the first place.

Glycemic Index: The glycemic index of foods as well as the fiber and fat content dramatically affect how quickly or slowly blood glucose level rises. (The glycemic index ranks foods based on how quickly they raise a person’s blood glucose.) One tip since most people’s blood sugar rises most quickly in the morning is to eat low glycemic foods at breakfast like yogurt or a bowl of oatmeal with a piece of fruit rather than foods with a higher glycemic index such as some cold cereals, pancakes, or muffins.

In general, foods and combinations of foods that have a low glycemic index and high fiber content will raise blood glucose more slowly. Conversely, foods with a high fat content tend to cause a delayed rise in blood glucose. The extent to which the glycemic index or fat content of a meal speeds or slows the rise in blood glucose following a meal varies from person to person. 

Meticulously timing your rapid-acting insulin dose and carefully calculating your dose according to the carbohydrate you will eat is usually best for blood glucose control, but it may not always be possible. There are times when you know exactly when and how much you will eat and times when you don’t. The following  tips may help you adjust for the realities of daily life:

High blood glucose before a meal. If your blood glucose is high before a meal, use how much your blood glucose level falls in response to one unit of insulin to calculate a dose of rapid-acting insulin to cover the high, then wait until that insulin begins to lower your blood glucose before you eat. 

Claudia Shwide-Slavin, a dietitian and certified diabetes educator in private practice in New York City, advises the following: “If your blood glucose level is between 140 mg/dl and 180 mg/dl, take the rapid-acting insulin and wait half an hour before eating. If it’s between 180 mg/dl and 200 mg/dl, wait 45 minutes. If it’s higher than 200 mg/dl, wait at least an hour.”  If a person is hungry or must eat at a specific time, Shwide-Slavin recommends limiting the amount of carbohydrate at the meal by eating mainly protein and nonstarchy vegetables.

Low blood glucose before a meal. If your blood glucose is low before a meal (below about 80 mg/dl), “Wait to take your insulin,” says Shwide-Slavin. “Let the food have 15 minutes to raise your blood glucose before taking your insulin.”

So, a few few more helpful hints to put your management “in the zone.” 



Learning more about timing insulin

I know a lot about diabetes and working with my insulin. But recently a friend sent me an article, “Rapid-Acting Insulin, Timing It Just Right”, written by well-noted certified diabetes educator and registered dietician, Hope Warshaw. It helped confirm some of what I know and helped clarify some of what I didn’t know about timing insulin with your meals. Here are some of the article’s highlights.

Warshaw points out that even when you think you’re doing everything right with your diabetes care regimen, your blood glucose levels can seem hard to control. One potential source of difficulty is how you time your injections of rapid-acting insulin with respect to meals.

Most diabetes experts recommend taking meal-time insulins (Humalog, Novolog and Apidra) within 15 minutes of starting a meal. This advice is based on the belief that rapid-acting insulin is absorbed quickly and begins lowering blood glucose quickly. However, this may not be true for everyone. 

Howard Wolpert, M.D., editor of the book Smart Pumping and Senior Physician and Director of the Insulin Pump Program at Joslin Diabetes Center, cautions against blind-faith acceptance of insulin action curves or standard advice about when insulin works, noting that insulin can show “a lot of variability…between individuals and even within the same person from day to day.” The time ranges given for an insulin to reach its peak action are averages, so they may not fit everyone or every situation. You may find through blood glucose monitoring and experience that rapid-acting insulin typically reaches peak effectiveness within 45–90 minutes or possibly sooner or later. In general, people with normal stomach emptying can expect some glucose from the carbohydrate they’ve eaten to start raising their blood glucose level within minutes of starting to eat. Blood glucose level tends to peak about one to two hours after the start of a meal and gradually drops over the next three hours.

If rapid-acting insulin always started working almost immediately and peaked one to two hours later, injecting it anytime within 15 minutes of starting to eat would work well. But newer observations suggest that rapid-acting insulin doesn’t get absorbed and start working that quickly in all people. John Walsh, P.A., C.D.E., coauthor of the book Using Insulin, for example, believes the maximum blood-glucose-lowering effect of rapid-acting insulin may occur much closer to two hours after an injection rather than 45–90 minutes. If this is the case, the optimal time to take rapid-acting insulin is 10 to 15 minutes before eating rather than with the first bite or 15 minutes after starting a meal. Walsh’s belief is based on research suggesting that insulin may be measurable in the bloodstream before it begins actively lowering blood glucose.


Some other factors that may cause insulin action to differ from the action curve given in product literature or to vary from person to person include thickness of the subcutaneous fatty layer at an injection site, temperature, blood flow, exercise, and dose size. (The choice of injection site—abdomen, thigh, arm, buttock—does not seem to affect the absorption rate of rapid-acting insulin as it does for slower-acting insulins.) Injecting into areas that have more subcutaneous fat tends to slow insulin absorption. Widened blood vessels (caused by higher temperatures or exercise) allow insulin to be absorbed more quickly; constricted blood vessels (caused by colder temperatures or smoking) can cause slower absorption. Large doses of insulin may also be absorbed somewhat more slowly than smaller doses.

Thank you Ms. Warshaw. Since this is a lengthy article there’ll be more from Hope’s article over the next few posts.