Why do some people living with type 1 diabetes need more insulin than others?

Insulin is a necessary, life sustaining medication for people living with type 1 diabetes (T1D). Today, there are many different kinds of insulin, different speeds of action, and methods to deliver insulin. Insulin needs are influenced by over 40 factors including exercise, food choices, and things that we have no control over like ambient temperature and life stage, meaning that everyone’s insulin use will be different over time and can change day to day. 

Insulin resistance in T1D?

One important factor that can change insulin needs is insulin resistance. When the body becomes less sensitive to insulin, more units of insulin are needed to achieve the same blood sugar results but this higher use can, in turn, worsen insulin resistance. While it is best understood as a major contributor to hyperglycemia in type 2 diabetes, insulin resistance and high insulin in the bloodstream may have important consequences in T1D. Certain factors are well-known to be associated with insulin resistance including physiological events like puberty or pregnancy, behaviours like sedentary lifestyle, or side effects of some medications (e.g., cortisone). Although it’s less talked about, insulin resistance may be an increasingly important metric for people living with T1D to understand their changing insulin needs and make management decisions.

A recent study from the BETTER registry investigated the spectrum of insulin needs and estimated insulin resistance in 1033 Canadians living with T1D to better understand their relationship to one another.

Daily insulin dose varies greatly among people living with T1D

In all HbA1c categories, participant’s daily insulin needs (total units per day by body weight) spanned the spectrum from low to high. However, the maximum insulin use was much lower among insulin pump users than people using multiple daily injections. Participants with higher HbA1c had higher insulin use on average; but there was very significant diversity. 

Insulin resistance and daily insulin dose 

To estimate insulin resistance, this study used a calculation that takes into account body mass index (BMI), high blood pressure, and HbA1c. While not a direct measure, it has previously been shown to correlate well with both precise measures of insulin resistance as well as a higher risk of some long-term complications in T1D (e.g. heart disease). 

Like with HbA1c, daily insulin needs spanned the entire spectrum in participants classified as low, mid, and high insulin resistance, indicating that this calculation does not take into account the exposure to insulin which could contribute to insulin resistance. 

What’s next?

This study clearly shows that the insulin needs for people living with T1D are extremely varied whether your HbA1c and insulin resistance are low or high. It also raises the question of if insulin resistance measures coupled with daily insulin that was used to reach the HbA1c could be better used as a clinical tool to personalize care. 

Regardless of insulin resistance, insulin remains a necessary medication for people living with T1D. Some lifestyle actions can certainly improve it like being more physically active and reducing abdominal fat. In terms of treatment, using an insulin pump or artificial pancreas may be a more efficient (e.g., use less insulin for the same blood sugar effect) method of insulin delivery than injections and some “adjuvant ” medications (e.g., Metformin, Ozempic and Mounjaro) approved for type 2 diabetes and weight loss may help to improve sensitivity to insulin in some select cases. 

Reference:

Messier V, Ramsay T, Rabasa-Lhoret R, Sun CJ. The spectrum of exogenous insulin requirement in people living with type 1 diabetes: A cross-sectional analysis. Diabetes Obes Metab. 2026 Apr;28(4):3411-3414. doi: 10.1111/dom.70467. Epub 2026 Jan 12. PMID: 41521907; PMCID: PMC12992158.