Since the introduction of Lilly's new, fast insulin called Humalog, many pumpers have been switching over. This is the first insulin produced since 1921 that can really cover most meals. Its fast action offers users more flexibility and more control. Humalog has not been cleared by the FDA for use in pumps, but some clinicians and pumpers have found this combination extremely useful. This article provides helpful hints for safety and success. 

The old Regular insulin 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. In the switch to Humalog, some surprises are likely. 

After switching from Regular to Humalog, some 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 their meal boluses are lowered they need to raise their basal rates to replace some of the lost meal dose. The bolus of Regular most people have been taking 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 noted they need extra basal 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. 

Humalog acts more like natural insulin. When given before most meals, it 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 nighttime basal insulin may also be needed to keep pre-breakfast readings down. 

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

Frequent blood sugar monitoring is especially important 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 1/2 hours after eating, and at any time unusual symptoms occur. This extra testing can prevent many problems caused by the new insulin dynamics. With extra testing, you can avoid severe hypoglycemia, and allow insulin doses to be quickly adjusted.

No longer do you need to wait 30 to 60 minutes after a bolus to eat meals as advised with Regular. Although with Humalog, a bolus is ideally taken 15 or 20 minutes before eating, you can control your blood sugar even when the bolus is taken with the first bite. 

But forget about delaying a meal. Humalog has little tolerance for delays. The major cause for severe low blood sugars is delayed eating, or becoming distracted and not eating. Because a blood sugar drop will start faster and fall more swiftly, any delay in eating after bolusing with Humalog can quickly become critical. If a delay in eating is planned to allow a high blood sugar to fall, be very careful that your delayed eating is not itself delayed. Be careful to eat as planned. On the other hand, those who have experienced severe lows, along with the one in five people with Type I 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. Those who in the past have had problems covering cold cereals or a scone for breakfast can now have great postmeal readings on Humalog. A new problem may arise with slower carbs, however, that were covered very well by Regular insulin. Meals like pasta al dente or a bean burrito will now be found to raise the blood sugar too slowly for Humalog. Eating foods that convert slowly to glucose can cause the blood sugar to go low at one or two hours after eating, but then rise after the Humalog is gone. Many dinner meals that were covered well in the past by Regular may now cause high blood sugars before breakfast the following morning. 

Certain meals may continue to be better covered with the old bottle of Regular. Those using Humalog in a pump as their only insulin may want to consider taking an injection of Regular instead of their Humalog bolus to cover slower meals. Again, checking the blood sugar often as you first go on Humalog to see the effect of different carbohydrate on the blood sugar. 

Because of Humalog's fast action, it is important to rely on fast carbs to treat Humalog lows. Fast carbs, like glucose, dextrose, or honey, may be required to reverse the rapid drops that can be encountered with this insulin. Several of JohnÕs patients and John himself have learned this lesson the hard way. 

Those who are using Regular insulin know they've really overdosed when a low blood sugar happens only two or three hours after a bolus. And they know that lows which happen five or six hours after a bolus of Regular usually do not require very much carbohydrate to treat. On the other hand, with Humalog, major lows are most likely to happen within three hours of the bolus. But when the blood sugar goes low at three or more hours after a bolus, 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 a person is on Humalog. By bedtime, the action of the Humalog taken for dinner is gone. Only a small amount of carbohydrate should be needed for a sound sleep. Under similar circumstances on Regular, extra carbohydrate would be needed to prevent another low later during the night. 

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 time as 45 minutes when the sliding scale insulin for the high reading has been added to the usual meal dose, and the meal is delayed, as mentioned above. 

On the other hand, if a blood sugar was normal before a meal but the blood sugar has risen above 200 mg/dl two hours later, those on a well planned control program would know their dose of Humalog for that meal was too low. And with Humalog's short action time of 3 1/2 hours, covering these postmeal highs with more insulin could be considered as early as two hours should a meal bolus be underestimated. Of course, not as much insulin would be needed in this situation as before a meal because not all of the previous bolus has been used. 

Most people find that less Humalog is needed to lower their high blood sugars. 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 bolus and basal 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 basal and bolus 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. Many users notice their blood sugars fall farther on each unit of Humalog. For safety, I (John) initially have my 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, doses closer to the 1500 Rule can, of course, be used. Again, be sure to discuss these anticipated changes carefully with your physician before switching over. Also test your blood sugar more often when first lowering high blood sugars with Humalog. 

On Humalog, determining the cause for a low or high blood sugar becomes easier. If afternoon lows are occurring on a pump with Humalog, only the lunch bolus or the basal insulin can be at fault. To find out which is the culprit, simply skip lunch and skip the bolus of Humalog ordinarily taken to cover it. If the blood sugar drops anyway, too much basal insulin is responsible. But if the blood sugar stays flat or varies by only 10 or 20 points when lunch is skipped, the basal is OK and the lunch Humalog has to be the culprit. 

On Humalog, it becomes easier to test basal rates. With Regular, it is necessary to stop eating and take no boluses for at least 5 or 6 hours before the last bolus of insulin has cleared the system, and is no longer affecting the blood sugar. At that time, the user can begin the basal test to determine if the basal rates are properly set. But on Humalog, boluses clear faster. Basal testing cas start 3 1/2 to 4 hours after the last bolus. 

This allows convenient basal testing without the need to fast for extended periods. If a bolus has been taken at 7 a.m. for breakfast, basal testing can start at 10:30 a.m. or 11 a.m. On Humalog, only lunch needs to be skipped to test the afternoon basal rates. 

The Unused Insulin Rule described in Pumping Insulin also changes. This rule lets you know how much residual insulin is left to work following a bolus. But instead of 16% or 20% of the insulin being used each hour with Regular, Humalog can be more closely approximated as 25% of the insulin being used per hour, or 4 hours of total action. For example, if 4 units of Humalog are taken at noon, 3 units will be left to work at 1 p.m., 2 units are left at 2 p.m., 1 unit is left at 3 p.m., and no further drop in the blood sugar would be expected from this bolus after 4 p.m. (Purists might say most of the bolus has been used in the first three hours, but the rule is designed to be conservative and to prevent the accumulation of excess insulin when boluses are overlapped.) The box to the right outlines other differences using Humalog in a pump. 

Finally, Humalog is here! For most people the benefits to good control are tremendous. To accomplish these benefits the challenge is learning some new techniques: greater attention to dosing, treating problems when they occur, and problem solving. Seek the advice of your health care provider and others using Humalog to shorten your learning curve. Test often as you switch over to avoid lows and better understand how Humalog works with you. And congratulate yourself on being a medical pioneer and taking charge of your blood sugar control. 

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