People with diabetes face a 1.5- to 4-fold increased risk of infection, according to a review by pmc.ncbi.nlm.nih.gov. This vulnerability stems from hyperglycemia’s impact on immune responses, increasing the likelihood of severe outcomes from respiratory, skin, and urinary tract infections, as well as life-threatening sepsis.
How hyperglycemia disables the immune response
The relationship between blood sugar and the immune system is not merely coincidental; it is biological sabotage. High blood sugar places constant stress on the body, forcing nearly every internal system to work harder to maintain equilibrium. This includes the white blood cells that serve as the body’s primary defense against bacteria, viruses, and fungi.
When glucose levels remain elevated, the immune system’s effectiveness drops. This impairment is compounded by a protective but damaging immune response known as inflammation. While inflammation is designed to protect the body, chronic inflammation in diabetic patients can damage internal organs over time. This creates a dangerous paradox: the immune system is simultaneously overworked and weakened, making it far harder to fight off common pathogens.
For those with type 1 diabetes, the risk is further complicated by the nature of the disease. Because type 1 is an autoimmune disorder—where the body mistakenly attacks its own tissues—the immune system may be fundamentally weaker from the start.
The specific threats: From S. pneumoniae to sepsis
Diabetes does not just make people “more likely to get sick”; it opens the door to specific, high-mortality infections. The risk is most pronounced in kidney infections, osteomyelitis, and foot infections. The latter is particularly insidious due to the combination of vascular insufficiency and neuropathy.
Neuropathy damages the nerves, meaning a patient may not feel a blister or cut on their foot as it happens. Without daily visual inspections, these minor injuries can escalate into deep-tissue infections. When combined with poor circulation in the lower legs, the body cannot deliver the necessary immune cells to the site of the injury, turning a simple scratch into a gateway for systemic infection.
The vulnerability extends to the respiratory system and beyond. According to the Sepsis Alliance, consistently high blood sugar lowers the ability to fight pneumonia, specifically that caused by Streptococcus pneumoniae.
- Gram-negative bacterial infections: Including salmonella, cat scratch disease, and pertussis (whooping cough).
- Fungal infections: Such as thrush or urinary and vaginal yeast infections.
- Common viruses: Including influenza and COVID-19, where the rate of death is twofold higher for people with diabetes.
These infections are not just complications; they are catalysts for sepsis, a life-threatening systemic response to infection that requires immediate medical intervention.
A1C levels and the 33 percent risk spike
Managing diabetes is often a balancing act, especially for older adults. Medical guidelines typically recommend more relaxed blood sugar targets for seniors to avoid the dangers of hypoglycemia (blood sugar becoming too low). However, this relaxation comes with a trade-off.
Research from Yale Medicine examined the association between different A1C ranges—6 to 7 percent, 7 to 8 percent, and 8 to 9 percent—and the risk of hospitalization for sepsis, respiratory, genitourinary, and skin/bone infections. While the higher end of the recommended range did not significantly increase the risk for most infections, a critical threshold exists at the top.
Individuals with A1C levels between 8 and 9 percent faced a 33 percent increased risk of hospitalization for skin, soft tissue, and bone infections. This suggests that while some flexibility in glucose control is necessary for the elderly, crossing the 8 percent A1C threshold significantly compromises the body’s ability to protect its structural tissues.
The scale of the U.S. prediabetes and diabetes epidemic
The clinical risks are amplified by the sheer number of people living with these conditions. The intersection of diabetes and infection is no longer a niche medical concern but a public health crisis.
“More than 100 million U.S. adults are now living with diabetes or prediabetes … The report finds that as of 2015, 30.3 million Americans – 9.4 percent of the U.S. population –have diabetes. Another 84.1 million have prediabetes, a condition that if not treated often leads to type 2 diabetes within five years.”
CDC, via Sepsis AllianceThis massive population is particularly vulnerable during pandemic cycles. While diabetes may not always increase the initial risk of contracting a virus like the flu or COVID-19, it drastically increases the risk of severe illness and death, especially when blood sugar is poorly managed.
Vaccination remains the most effective tool for mitigation. However, the efficacy of some immunizations can be compromised by hyperglycemia, making tight glycemic control a prerequisite for the vaccines to work as intended.
For those living with these conditions, the path forward requires a combination of aggressive monitoring and preventative care. This includes daily foot checks to prevent “silent” injuries and staying current on all eligible boosters to compensate for a weakened immune response. Always consult your healthcare provider for personalized treatment plans and glycemic targets.
