An acquaintance states that in a recent purchase of insulin syringes, made by the leading US manufacturer of insulin syringes, she perceived (visually) that several syringes from the same box had a noticeably larger “gap” between the “zero” mark and the top end of the barrel. Based on that observation, my colleague suggests that “allowable manufacturing tolerances” could allow for more, or less, insulin to be drawn up in the syringe than one would believe one was drawing up based on unit marks. That is, if one were drawing up 1 unit, more or less of a gap could result in more or less than 1 unit.

I assert that as FDA-regulated medical devices, such wide tolerances and/or manufacturing sloppiness would not be allowed in the manufacture of insulin syringes, and that if a difference in the amount of “gap” (as defined above) existed, then there is some other factor (such as within the hub) that is not visible, that still results in an accurate dose (i.e., 1 unit is 1 unit). Can you please comment on this?

Because insulin syringes have to meet strict FDA guidelines for accuracy, leading manufacturers enforce strict quality control standards. In my 25 years of experience taking care of thousands of people with diabetes, I have never heard this complaint before. That means it must be very rare, and I wouldn’t worry about it happening again any time soon.

JS
Additional comments from Dr. Donough O’Brien:

The problem you describe has been observed occasionally in situations where the syringe manufacture appears to have been subcontracted by one of the big chain stores. It has not been encountered with those made by leading manufacturers.

Your friend should certainly bring this to the notice of the supplier, but in the meantime should only use an established brand.

DOB
Additional comments from Dr. Tessa Lebinger:

I don’t know what the FDA allowance is in accuracy of insulin syringes, but I would suggest that your acquaintance contact the manufacturer and send back a syringe to be evaluated. If he or she is not satisfied with their evaluation, your friend can contact the FDA and ask them their opinion and advice.

TGL
Additional comments from Dr. David Schwartz:

Yes, large variations are seemingly a concern, and while I think that if you or your friend have questions about the insulin syringes, you should take the supplies back to the pharmacy where purchased and speak with the pharmacist. In addition, you should contact the manufacturer!

Having said that, I am uncertain what degree of variability is allowed, but for purposes of this example, let us say that a full 20% variability is “allowed” by regulatory agencies. (I actually presume that much tighter standards are in force, but I am using this wide variance on purpose.) So, if that “extra gap” was not actually the 1.0 unit, but rather 1.2 (or 0.8 units -i.e. +/- 20%) the absolute difference in insulin is really clinically negligible for most people with diabetes, except perhaps the youngest of children. Certainly, if the entire syringe were off by 20% (but that is not what you describe), then 100 units could really range from 80-120 units and that would be a large and unacceptable variance.

DS
Additional comments from David Holtzman:
Questions regarding the safety of medical devices like syringes should be directed to the FDA. See Reporting Problems with Medical Devices.

DH