Question: How can you tell if the insulin in any given vial is still good before injecting it?

Answer: You can't! You have to "test" it on yourself by injecting and awaiting the blood sugar results.

Isn't that crazy?!

A reader emailed me a week or so ago asking why there is no litmus test — like a strip of test paper where applying a few drops of insulin would yield either green for "good" or red for "bad"  — to tell whether the insulin is active or not active.

Well, why isn't there? I thought.  It's got to be either a cost issue (too expensive to produce and market), or not yet scientifically possible. I find the latter hard to believe.

So what did I do?  I queried the big three manufacturers of insulin in this country, that's what.  Here's how the various heads of PR answered my query:


There are chemistry tests that can be run in a lab to determine insulin activity, but it's not something that can be appropriately replicated outside a lab setting, and there currently are no such tests available for patients. The best advice we can provide is that anytime a person has a question about his/her insulin, call the physician and the call center associated with the product (for Lilly insulins, it's 1-800-LILLYRX). The call center can direct the person to the appropriate resources, and step them through the product complaint process if necessary.

Also, one of our physicians, Dr. Sherry Martin, added this:

"As a practical note, physicians tell patients to take a dose from a new vial or pen (the patient should have one backup on hand): if the blood glucose improves, they have the answer they need in a matter of hours. Then, they can discard the old vial/pen.  If it doesn't improve, call your HCP and hold on to all insulin you have."


Novo Nordisk has conducted extensive stability studies on our insulin products to ensure that they maintain potency throughout their entire lifetime, from manufacture through shipping and storage until the labeled expiration date.

If your insulin is kept in accordance with the guidelines on the label, the product should maintain expected potency.  Novo Nordisk cannot evaluate specific cases outside of the recommended storage.  If you chose to administer insulin that may have been improperly stored, then it is important to monitor your blood glucose to ensure your readings are within the goals determined by you and your healthcare professional. Prior to injecting your insulin, the insulin should be inspected for changes, such as clumping, frosting, precipitation, or change in color or clarity that may indicate a loss in potency.  However, a lack of visual changes is not a guarantee of the potency of improperly stored insulin.

Novo Nordisk is continuously evaluating changes in packaging that may help identify insulin that has been improperly stored or to protect it from changes in the storage environment.

I have sent your reader's idea to our product design department in Denmark for consideration.


Unfortunately, the tests currently available for determining insulin activity are not practical for home use. In the absence of such a test, Sanofi-Aventis' goal is to ensure that the insulin that reaches the patient has the expected activity through good manufacturing, testing, and shipping practices. At home, proper storage and regular inspection before use are key to maintaining and delivering insulin with the expected potency.

It is important to note that both of the insulins we manufacture are clear and colorless, so if you are using a Sanofi-Aventis insulin product and your insulin appears cloudy or colored, or if you have any other questions about your insulin, please contact your treating healthcare provider or our Medical Information Services at 1-800-633-1610.


The upshot is: there is no such test. We're on our own (especially suck-ish in the summer heat).  But at least they've all made note of my query.  It never hurts to be the squeaky wheel.  So if a test like this seems important to you, email me and I'll point you where to lobby. Human guinea pigs, unite!

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This content is created for Diabetes Mine, a consumer health blog focused on the diabetes community. The content is not medically reviewed and doesn't adhere to Healthline's editorial guidelines. For more information about Healthline's partnership with Diabetes Mine, please click here.