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November 14, 2001


Question from Yukon, Oklahoma, USA:

We kept getting high blood sugar levels so we finally just tried another bottle of Humalog in the pump, and the numbers went back to normal. Now that bottle is in question. Is there a test or a way to know if the insulin is working and is as potent as another bottle of the same insulin?


From: DTeam Staff

The bottle isn’t in question — the insulin is! Humalog goes bad after it has been open for a month for sure and often sooner. Are you getting your insulin by mail order? If yes, that can be a problem. Insist on overnight delivery in a cooler, and reject it if the cool pack isn’t cold.

I see or hear from a patient nearly every day who finds insulin having gone bad. It just happens. A few unexplained highs equals a new vial of insulin or a new pen.


[Editor’s comment: I’m unaware of any way to test if a bottle of insulin has “gone bad” except by appearance: if it’s a clear insulin like Humalog or Lantus (insulin glargine) and it has particles or a cloudy appearance, don’t use it; if it’s a suspension (like NPH) and it has a layer of “frosting” on the inside of the bottle, or clumps of insulin, again don’t use it. (Don’t just throw it away — contact your pharmacy or the manufacturer for a refund or replacement.)

Of course, the other way to tell a bottle of insulin is “bad” (less potent) is in hindsight — if after switching to a new bottle, there’s immediate improvement in blood sugar numbers on the same dose of insulin.