Humalog is a terrific insulin that improves postmeal readings, reduces the frequency of lows, and generally makes people feel better. But reports from people on both pumps and injections have surfaced indicating that Humalog has trouble handling the heat. These reports began to appear just after Humalog was released.
Most insulins are relatively stable in hot weather, and lose potency only with unusually high temperatures (i.e., a non-refrigerated delivery truck with a flat tire in Phoenix in August). However, Humalog has gained a reputation for wanting to stay in your refrigerator, raising concerns about how your insulin is handled in transit to your pharmacy or home.
Is Heat Really A Problem?
Users report random, unexpected high blood sugars that correct when a new bottle of Humalog is started. Inspection of the bad bottle reveals either 1) several very tiny particles, much smaller than those typically found in a bad bottle of Regular, 2) one or two large hazy particles, or 3) small particles attached to the insides of the bottle. Healthy Humalog will appear as pure as clear water, with no particles or haze.
Insulin pumps may be especially prone to unexpected highs because they use only Humalog. Heat-related problems typically start after three to four days use in a pump, or, when a bad bottle is encountered, immediately after first use of that bottle. On injections, the problem typically shows up as unexpected high readings after meals.
Research studies undertaken so far have indicated no problem with use of Humalog in pumps. Prior to Humalog's release, Lilly conducted extensive heat and stability testing, and believed that it was as stable as Regular insulin which has an excellent history. But in the larger lab of the world, a loss of activity due to heat appears to occur, especially in hot weather.
The problems being reported with pumps may, of course, be due to unrelated factors like leaks or clogs. But veteran users, who know how to sort out mechanical from non-mechanical sources, believe there is a problem. Problems may be more apparent in pumps due to the interaction of the insulin with plastic surfaces, lubricants or other environmental conditions, as well as the warmer temperatures. Although it is not a common problem, we believe these are not just anecdotes because we have heard too many reports from reliable pump users.
What Can You Do?
First, be aware of the problem. If you experience unexpected highs on Humalog, inspect your insulin immediately. Request that any Humalog you receive be refrigerated during the entire shipment process, and that any mail order deliveries be packed in ice. Inspect bottles before use. John Walsh, PA. CDE, has had several experiences with patients and personally, including one bottle that was bad (high blood sugars, particles in the insulin on inspection, and no correction after an injection) on receipt from a local pharmacy. Other bottles in the same order were fine.
Some pumpers report that the stability of Humalog appears to improve in their pumps when Humalog is mixed 3 to 1 or 2 to 1 with another insulin called Novo-Nordisk Velosulin Regular. Velosulin, like Humalog, is a phosphate buffered insulin that has been used for years in insulin pumps without problems. The mixture of Velosulin Regular with Humalog would be expected to slow the action of Humalog slightly, but users seem to prefer this apparent stability to the slight delay.
Lilly currently recommends that Humalog be continuously refrigerated or kept in an iced container. Both insulin pump companies in the U.S. are aware of user's reports from users. If you have had a problem with inactive Humalog due to heat or for any reason, send the suspect insulin to Lilly for analysis. Also read other user's reports.
For additional information on Humalog and intensive management, carbohydrate counting, glycemic index, proper insulin doses, or exercise, get Pumping Insulin and the Pocket Pancreas by John and Ruth, or Using Insulin by John, Ruth, and C Varma MD, T Bailey MD