Are People With Type 1 Diabetes Immunocompromised?
Are People With Type 1 Diabetes Immunocompromised?
The short answer is no. The longer answer is the useful one — and it changes how you think about a sick day.
Type 1 diabetes is an autoimmune disease. It is not an immunodeficiency. Those two words get used as if they point at the same problem, and they are closer to opposites.
An immunodeficiency means the immune system is missing something it needs. Type 1 is the other failure. CDC describes it as an autoimmune disorder — the immune system mistakenly attacking part of the body. The system worked, aggressively and precisely, and aimed itself at the beta cells. Nothing in that process leaves a person short on defenses against a head cold.
So why does the question keep coming back? Because the honest answer has a “however” attached to it, and that however is worth understanding. It decides how you handle a sick day, what you say to a school nurse, and which box you land in on a vaccine form.
What high blood sugar does to immune cells
Here is the part that gets flattened into “diabetics are immunocompromised.” Sustained high blood sugar does blunt immune function. But it does it as a state, not as a trait.
Zhou and Lansang, reviewing the topic for Endotext, lay out the specific machinery. Neutrophils are recruited less well and produce less hydrogen peroxide, which is part of how they kill bacteria. Glycosylation of complement protein C3 impairs its ability to attach to pathogen surfaces. In vitro, advanced glycation end products block neutrophils from migrating out of the bloodstream toward an infection. A separate finding on macrophages — impaired receptor pathways for engulfing pathogens — was observed in cells from people with type 2 diabetes, so it does not carry over to Type 1 without more evidence.
The word that matters there is “state.” These are defects that move with glucose, not permanent properties of the diagnosis. But don't push that too far. The review's evidence that lowering glucose helps comes from hospital settings — a cardiac surgery protocol where tighter post-operative glucose tracked with fewer deep wound infections. It also flags the counterexample: in the NICE-SUGAR trial, driving glucose down hard with IV insulin in intensive care increased deaths, through hypoglycemia. The association is well described. A dose of glucose-lowering that reliably repairs it is not.
It also explains why illness is dangerous in a way that has very little to do with catching more colds.
What the research actually shows
The strongest evidence here comes from cohort studies, which describe association rather than cause. Carey and colleagues, writing in Diabetes Care in 2018, matched 5,863 people with Type 1 against 11,696 people without diabetes in English primary care records and counted infections from 2008 to 2015. One limit to hold onto: the cohort was restricted to people aged 40 to 89 whose diabetes was diagnosed by 2008, so it is not a picture of children or of newly diagnosed adults.
What they found is a gradient, and the shape of it is the real answer to the question. Infections needing a prescription came in modestly higher in the Type 1 group — an incidence rate ratio of 1.66. Infection-related hospitalization came in at 3.71. Infection-related death came in at 7.72, but that rests on 80 deaths, and the confidence interval runs from 4.47 to 13.33 — a threefold spread, which is the study telling you how much it does not know.
So it is not that people with Type 1 catch far more things. It is that the serious end of the range is heavier. The authors name an alternative reading worth sitting with: some of the gap could reflect a greater tendency to diagnose, prescribe, admit, or code a death as infection-related once a diabetes diagnosis is on file.
The part nobody has separated
Every number above comes from observational data, and observational data is not built to tell you why. Two explanations fit the same findings, and the studies were not designed to referee between them. They are not mutually exclusive — most likely both contribute, and nobody has measured how much of the gap belongs to each.
What the research can show is that the association exists and that, for infection-related hospitalization, it is graded — higher HbA1c, higher risk, band by band. What no cohort study can show is how much of that gap would close if glucose alone changed. That question is still open.
The immune system in Type 1 is not weak. It can be slowed down — and what slows it down is the same thing that makes everything else harder.
What this means when you are the one who is sick
The label matters in a few specific places. “Moderately or severely immunocompromised” is a defined clinical category with a specific list behind it — transplant recipients, people in active cancer treatment, primary immunodeficiencies, certain immunosuppressive drugs. CDC does not include diabetes of either type on that list, though it does say the list is “not limited to” those conditions. And on the question people ask most, CDC is unusually direct: people with diabetes might not be more likely to catch COVID or flu, but research shows they are at increased risk of severe illness from them.
One honest wrinkle: a different CDC page says that because Type 1 is autoimmune, people with it “may have weaker immune systems.” That sits awkwardly beside the immunocompromised list that leaves diabetes off, and CDC does not reconcile the two. If a clinician quotes one page at you and you have read the other, that is why.
That distinction is worth carrying into the conversation with a school nurse, an HR department, or the appointment where someone waves a hand and says immunocompromised. You are not describing a broken immune system. You are describing a condition where getting sick is more likely to go sideways, and where a large part of what decides how sideways is glucose — the part that is within reach. None of that is a reason to change anything about your care on your own. A sick-day plan is a conversation to have with your doctor before you need it, not during.
Infection risk in Type 1. Carey IM, Critchley JA, DeWilde S, Harris T, Hosking FJ, Cook DG. Risk of Infection in Type 1 and Type 2 Diabetes Compared With the General Population: A Matched Cohort Study. Diabetes Care, 2018;41(3):513–521. Retrospective cohort: 5,863 people with Type 1 vs 11,696 age-, sex- and practice-matched controls, English primary care (CPRD), 2008–2015, ages 40–89 with diabetes diagnosed by 2008. Unfunded; authors reported no conflicts.
HbA1c and infection risk within Type 1. Critchley JA, Carey IM, Harris T, DeWilde S, Hosking FJ, Cook DG. Glycemic Control and Risk of Infections Among People With Type 1 or Type 2 Diabetes in a Large Primary Care Cohort Study. Diabetes Care, 2018;41(10):2127. 4,496 people with Type 1, follow-up 2010–2015. Described by the authors as an unfunded study. This is the source for the graded HbA1c relationship — not the COVID data below.
How high glucose affects immune cells. Zhou K, Lansang MC. Diabetes Mellitus and Infection. Endotext, NCBI Bookshelf, last updated June 2024. Narrative review of mechanism. Note that its macrophage findings are drawn from cells of people with type 2 diabetes, its advanced-glycation finding is in vitro, and its evidence that lowering glucose improves outcomes comes from perioperative and inpatient settings rather than everyday outpatient management. The chapter does not describe people with diabetes as immunocompromised; it describes specific, partial immune defects.
Illness outcomes and HbA1c. Holman N, Knighton P, Kar P, et al. Risk factors for COVID-19-related mortality in people with type 1 and type 2 diabetes in England: a population-based cohort study. The Lancet Diabetes & Endocrinology, 2020;8(10):823–833. 264,390 people with Type 1, 464 COVID-19-related deaths, 16 Feb to 11 May 2020. Hazard ratio 2.23 (95% CI 1.50–3.30) for HbA1c at or above 86 mmol/mol (10.0%) versus 48–53 mmol/mol (6.5–7.0%). Important: in Type 1 the elevation reached significance only in that highest band; the stepwise gradient across all bands was found in type 2 diabetes.
Infection as a trigger for ketoacidosis. Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycaemic crises in adults with diabetes: a consensus report. Diabetologia, 2024;67:1455–1479. Source for the finding that infection is the most common precipitant of DKA worldwide, occurring in 14–58% of cases, and for insulin omission dominating in US cohorts. The counterregulatory hormone mechanism is described in Dhatariya K, Mustafa OG, Stathi C. Hyperglycemic Crises. Endotext, NCBI Bookshelf, 2025.
Co-occurring autoimmune conditions. Nederstigt C, Uitbeijerse BS, Janssen LGM, Corssmit EPM, de Koning EJP, Dekkers OM. Associated auto-immune disease in type 1 diabetes patients: a systematic review and meta-analysis. European Journal of Endocrinology, 2019;180(2):135–144. 180 articles, 293,889 people with Type 1.
What CDC says. COVID-19 Vaccination Guidance for People Who Are Immunocompromised (last updated November 2025) and Your Immune System and Diabetes (last reviewed December 2023, last updated May 2024), US Centers for Disease Control and Prevention.
How to read this evidence. The infection and mortality figures come from cohort studies. A cohort study shows that two things occur together in a population; it does not establish that one causes the other, and it can only adjust for the factors the researchers measured. The mechanism descriptions come from narrative reviews, which summarize a field rather than test a hypothesis. The autoimmune prevalence figures come from a systematic review and meta-analysis, which is the strongest tier used here. No randomized trial in Type 1 diabetes has been designed to test whether lowering blood sugar reduces infection risk; that link rests on observational data. The closest randomized evidence comes from intensive-care insulin trials in mixed, mostly non-Type 1 populations, and those results conflict — one found fewer bloodstream infections, a larger one found no difference and more deaths.
This post is for educational purposes only and is not medical advice. Nothing here is a recommendation to start, stop, or change any medication. Talk with your doctor before making any changes to your care.
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