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October 10, 2004


Question from Broken Arrow, Oklahoma, USA:

My daughter has been having more highs and lows than normal. I heard this could be because of insulin crystals. What are insulin crystals and where do they come from?


What a neat question.

I think there are two answers, depending on what you’ve read. You’ll see. Read on.

When insulin is given subcutaneously, the insulin molecules “connect” in a way that can form microscopic “crystals”. Depending on the size of these connections, the absorption of insulin can be interfered with as the “non-crystallized” insulin is absorbed faster and more efficiently. This is part of the basis of the development of the newer insulin analogues, particularly lispro (Humalog) insulin and aspart (NovoLog) insulin. Their molecular make up has been altered to switch and or exchange amino acids which affects how the insulin molecules connect and thus reduces crystallization. As such, the insulin can be absorbed more quickly!

Another possible reference to your answer lies in your bottle of insulin at home: old, deteriorated insulin begins to “clump” or “frost” or “crystallize” in your bottle. If your bottles of clear insulin (Regular, Humalog, NovoLog, or Lantus) look in any way “frosted” on the inside, that is crystallized insulin and that insulin is not as good. Similarly, if your bottles of cloudy insulin (NPH, Lente, UltraLente) look “clumpy” on the inside, toss that no good insulin out as it will be less effective.