How can I accurately measure 1/2-unit doses of insulin for my young son?

William Lee Dubois
Endocrinology Diabetes & Metabolism
Both Novo Nordisk and Eli Lilly make ½ unit insulin pens. These are wonderful metal pens that take disposable “penfills” that hold 300 units of insulin. Penfills are made for both fast-acting and basal insulin.

Either pen uses a dial on the base to select the dosage. Both pens deliver in half units and full units, so it is possible to deliver, say 2.5 units of insulin. To use, you simply dial up the dose, then push the base of the pen in with your thumb. Easy peasy.

The business end of the pen uses what is called a pen needle, a specially designed short needle that screws onto the tip of the pen the way you screw the cap back on your car’s tire after checking the air pressure. Needles come as thin as 33 gauge and as short as 3/16 of an inch. That’s very, very small.

The pen lasts for years. The penfill lasts a couple of weeks to a month. The pen needles last between a day at the most and a single shot at the least (depending you your insurance and bank account balance).

Novo’s NovoPen Junior is slim and painted in bright funky colors to make it kid-friendly. Lilly’s HumaPen Luxura HD is a bit larger, in forest green, and has a mechanism that reminds me of a Swiss watch or German camera: solid and mechanically perfect.

It is helpful to use low-dose (50-unit) or very-low-dose (30-unit) syringes when measuring small amounts of insulin because these syringes are narrower and have an expanded scale on the barrel. Syringe attachments that magnify and make it easier to read the scale are also available in many pharmacies. In addition, insulin manufacturers will provide diluting fluid if necessary for more accurate measurement.

Many children are extremely sensitive to insulin, and it is not unusual for doctors to prescribe 1/2-unit doses of insulin for such patients. One recent study determined how accurately the parents (caretakers) of young children with diabetes were able to prepare very small doses of insulin. The results of this study suggest that people do not measure insulin very accurately in 1/2-unit doses.

Interestingly, the study also found that people tend to overestimate the dose and deliver more insulin than they are supposed to. The good news is that each person tends to overestimate by the same amount nearly every time. So small children with diabetes may need to have only one caretaker who prepares their insulin injections to keep measurements consistent.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.