by John Walsh, P.A., C.D.E., and Ruth Roberts, M.A.
Copyright--1996 by Diabetes Services, Inc.


The new, fast insulin Humalog, is finally here. Since the introduction of Lilly's new insulin, many people have been switching over. This is the first insulin produced since 1921 that can really cover most meals, and its speed of action offers users more flexibility and control. This article provides helpful hints for safety and success when starting this new product.

Almost everyone who is switching to Humalog is doing so to replace their Regular insulin. Regular is often thought of as "meal" Regular or "high blood sugar" Regular, but its action time of five to eight hours more closely resembles a long-acting insulin.

After switching from Regular to Humalog, many people have found that fewer units of Humalog are needed to cover the same food. Fewer units may also be needed to lower high blood sugars. Others have discovered that as meal doses are lowered, they need to raise their long-acting insulin to replace some of the lost meal dose.

The Regular insulin most people take for breakfast has, in effect, been lowering their after-lunch blood sugars as well. This prolonged action is no longer seen with Humalog. Several of my (John's) patients and several diabetes colleagues have found they need extra long-acting insulin in the morning after switching in order to keep the afternoon and pre-dinner readings down. Another alternative is to use extra Humalog to cover lunch.

When given before most meals, Humalog will cover these meals only during the time they are raising the blood sugar. Its action is gone before the next meal begins, and most importantly for many, before going to bed. This eliminates many nighttime lows. But with the loss of the longer action of the dinner Regular, more evening long-acting insulin may also be needed to keep pre-breakfast readings down.

These significant timing differences between Humalog and Regular often require that doses be modified. Rarely can you simply replace Regular with Humalog. Before starting on this new insulin, doses should be carefully discussed with your physician. Some things to consider:

Test Often

Monitor blood sugars often when switching to this particular insulin. Due to Humalog's fast onset of action, routine testing is recommended before each meal, at 2 to 2 � hours after eating, and at any time unusual symptoms occur. Extra testing can prevent many problems caused by the new insulin. And this extra testing can help you avoid severe hypoglycemia by allowing you and your physician to quickly adjust insulin doses as needed.

Eat Differently

No longer do you need to wait 30 to 60 minutes after an injection to eat meals as advised with Regular. Depending on premeal blood sugars, Humalog can be injected 20 minutes before a meal, or with the first bite of food. Remember, though, that delayed eating is the most frequent cause of severe hypoglycemia. Because blood sugars fall more swiftly with Humalog, any delay in eating after an injection can quickly become critical. If a delay in eating is planned to allow a high blood sugar to fall, be very careful not to delay too long. Eat as planned!

On the other hand, those who have experienced severe lows, along with the one in five people with type 1 diabetes who experience Hypoglycemia Unawareness, will be glad to find they can now take their Humalog along with their first bite of food. This simple procedure can prevent many severe lows and all of those related to delayed eating.

High glycemic index foods are no longer a problem. If you have had problems covering cold cereals or a scone for breakfast, you can now have great postmeal readings. But with slower carbs like pasta al dente or bean burritos you might experience hypoglycemia before the food digests. The blood sugar may fall at one or two hours after eating, but then rise after the Humalog is gone. Many dinner meals that were previously covered well by Regular may now cause blood sugars to rise before breakfast the following morning. Certain meals may continue to be better covered with the old bottle of Regular. Check the blood sugar often as you first go on Humalog to see what impact different carbohydrates are having on your blood sugar.

Treat Lows Differently

Because of Humalog's fast action, it is important to rely on fast carbs to treat Humalog-induced lows. Fast carbs, like glucose, dextrose, or honey, may be required to reverse the rapid drops that can be encountered with this new insulin. Don't learn this lesson the hard way.

If you are using Regular insulin, you know you've overdosed when a low blood sugar happens only two or three hours after an injection. And you know lows that happen five or six hours after an injection of Regular usually do not require much carbohydrate to treat. With Humalog, major lows are most likely to happen within three hours of the injection. But when the blood sugar goes low at three or more hours after an injection, most of the Humalog is gone, and 10 to 15 grams of carbohydrate is likely to remedy the problem.

Low blood sugars at bedtime are also easier to treat when you are on Humalog. By bedtime, the action of the Humalog taken for dinner is gone and only a small amount of carbohydrate should be needed for a sound sleep. With Regular, extra carbohydrate would be needed to prevent another low later during the night.

Treat Highs Differently

The dynamics of action for Humalog are quite different from other insulins. High blood sugar readings in the 300 range, for instance, can now be lowered to normal in as little as 45 minutes when the sliding scale insulin is added to the meal insulin and the meal is delayed to allow the blood sugar to fall.

And if a blood sugar was normal before a meal but has risen above 200 mg/dl two hours later, those on a well planned control program know immediately they needed more Humalog for the meal. With Humalog's short action time of 3 � hours, covering postmeal highs with more insulin can be considered as soon as two hours if a meal dose have been underestimated. Of course, not as much sliding scale insulin would be needed here as before a meal, because some of the meal dose is yet to work.

Many people have found that less Humalog is needed to lower high readings. The 1500 Rule developed by Dr. Paul Davidson of Atlanta gives a very close approximation for how far the blood sugar will drop in mg/dl for each unit of Regular. To determine how far the blood sugar will drop, simply count the total number of units of long and short acting insulin used during an average day. Then divide this total daily insulin dose into 1500 to find the point drop in mg/dl a person can expect per unit of Regular. For instance, someone who uses a total of 30 units of Regular and long-acting insulin each day would divide 30 into 1500. They are likely to drop 50 mg/dl on each unit of Regular. For each 50 mg/dl they are above their target blood sugar before meals, they would add an extra unit of Regular to their usual insulin dose to correct the high blood sugar.

However, Humalog's fast action changes this formula. Most users notice their blood sugars fall farther on each unit of Humalog. For safety, I (John) initially have patients replace the 1500 Rule for Regular with an "1800 Rule" for Humalog. Someone on 30 total units a day would now divide 30 into 1800 to find their blood sugar is likely to drop 60 mg/dl on each unit of Humalog, rather than the 50 mg/dl drop seen with each unit of Regular. If these reduced doses do not bring the blood sugar down, sliding scale doses closer to the 1500 Rule can, of course, be used. Again, be sure to discuss these anticipated changes carefully with your physician and remember to test your blood sugar more frequently as you start using Humalog.

Sleuth Differently

On Humalog, determining the cause for a low or high blood sugar becomes easier. Most people who use a multiple injection program with Humalog use a morning long-acting, an evening long-acting, and Humalog before each meal and to lower highs. If afternoon lows are occurring on a multiple injection program with Humalog, only the lunch Humalog or the morning long-acting insulin can be at fault.

To find out which is the culprit, simply skip lunch and skip the dose of Humalog ordinarily taken to cover it. If the blood sugar drops anyway, too much long-acting insulin is being taken in the morning injection. But if the blood sugar stays flat or varies by only 10 or 20 points when lunch is skipped, the morning long-acting dose is OK and the lunch Humalog has to be the culprit.

The evening long-acting insulin could also be the culprit, but setting the dose of this insulin depends primarily on the breakfast blood sugar and becomes easier to do.


What if the before breakfast blood sugar is now going too high on Humalog? The dinner Regular taken in the past may have been working for 6 to 8 hours. This Regular may have been acting as a long-acting insulin. More long-acting insulin may be needed in the evening on Humalog, but be sure to test in the middle of the night until correctly set! To cover complex carbs or high protein foods at dinner, try using Regular rather than Humalog to better match their slow release of glucose during the night.

Tips For Using Humalog


Finally, Humalog is here! For most people the benefit to good control is tremendous. To accomplish these benefits the challenge is to pay greater attention to proper doses, treat problems quickly when they occur, and to use new problem-solving techniques. Seek the advice of your health care provider and others using Humalog to shorten your learning curve. Test often as you first switch over to avoid lows and better understand how Humalog works for you. And congratulate yourself on being a medical pioneer who is taking charge of your blood sugar control.

This article was written by the authors of "STOP the Rollercoaster" (with Dr. Lois Jovanovic-Peterson), "Pumping Insulin, My Other CheckBook", and the new ON-TRAC Record System, all published by Torrey Pines Press. To order these books containing the latest information on blood sugar control methods, the prevention and reversal of complications, carb counting, or a free catalog, call The Diabetes Mall at 1-800-988-4772. Browse their comprehensive diabetes site for information on diabetes books and software at