Diabetes does not directly cause fever the way an infection does, but it creates several conditions that can lead to elevated body temperature or make you far more likely to develop infections that do cause fever. If you have diabetes and notice a fever, it almost always signals that something else is going on, and your diabetes is likely making it harder for your body to handle it.
How Diabetes Affects Body Temperature
High blood sugar disrupts your body’s ability to regulate its internal temperature in a few overlapping ways. When glucose levels climb, blood plasma becomes more concentrated, which independently impairs sweating and blood flow to the skin. These are two of your body’s primary cooling mechanisms. At the same time, high blood sugar triggers a cycle of excessive urination that pulls fluid from your body, leading to dehydration. The combination of concentrated blood and low fluid volume compounds the problem, making it significantly harder for your body to shed heat.
Both type 1 and type 2 diabetes are associated with a reduced ability to maintain normal core temperature during heat stress. Over time, nerve damage from diabetes (a condition called autonomic neuropathy) can also alter the sweating response. In some people with diabetic neuropathy, the internal temperature at which sweating kicks in is higher than normal, meaning the body waits too long before activating its cooling system. While compensatory heavy sweating in unaffected areas can sometimes make up the difference, the overall pattern of temperature regulation becomes less reliable.
None of this means diabetes produces a true fever in the classic sense. But it does mean your body runs hotter more easily and cools down less efficiently, which can feel like a low-grade temperature increase during warm weather, exercise, or illness.
Why Infections Are More Common With Diabetes
The more important link between diabetes and fever is infection. People with diabetes get infections more often, and those infections tend to be more severe. This is where fever most commonly enters the picture.
High blood sugar weakens the immune system at multiple levels. White blood cells called neutrophils, which are your first responders against bacteria, become less effective. They produce fewer of the reactive molecules they normally use to kill pathogens, they’re slower to reach the site of infection, and they have trouble engulfing bacteria. Meanwhile, the signaling molecules that coordinate your immune response are suppressed. Your body produces less of the chemical messengers that activate different branches of the immune system, leaving gaps in its defense.
The result is a measurably higher risk for several specific infections:
- Urinary tract infections, one of the most common infections in people with diabetes, partly because sugar in the urine creates a favorable environment for bacteria.
- Pneumonia and lower respiratory tract infections, caused by a range of bacterial pathogens. People with diabetes are hospitalized for pneumonia at higher rates than the general population.
- Skin and soft tissue infections, including diabetic foot infections and abscesses, which can develop from minor wounds that heal slowly.
- Fungal infections like mucormycosis and aspergillosis, which are rare in healthy people but disproportionately affect those with poorly controlled diabetes.
Any of these infections can produce fever. In people with diabetes, the fever itself then creates an additional problem: your immune system releases stress hormones to fight the illness, and those hormones push blood sugar even higher. Higher blood sugar further weakens the immune response, creating a cycle that can be difficult to break without deliberate management.
Fever as a Sign of Serious Complications
Two dangerous diabetes-related emergencies can involve fever, and both require immediate attention.
Diabetic ketoacidosis (DKA) occurs when the body can’t use glucose for energy and starts breaking down fat at a dangerous rate, producing acidic byproducts called ketones. DKA is most common in type 1 diabetes, and infection is one of its most frequent triggers. When DKA develops alongside an active infection, fever is often present. People already in DKA also have a harder time fighting off whatever infection triggered the crisis, which can escalate quickly.
Hyperosmolar hyperglycemic state (HHS) is more common in type 2 diabetes and involves extremely high blood sugar, often above 600 mg/dL, with severe dehydration. Fever above 100.4°F (38°C) is a recognized finding in HHS, alongside confusion, extreme thirst, weakness, and rapid heart rate. HHS can develop over days or weeks and is a medical emergency.
Managing Fever When You Have Diabetes
If you develop a fever, monitoring becomes critical. The CDC recommends checking your temperature every morning and evening during any illness, since fever may be your first clue that an infection is developing. Weigh yourself daily as well: unexpected weight loss during illness is a sign that blood sugar is running too high.
Try to eat as normally as possible and stay hydrated. Your blood sugar will likely run higher than usual while you’re sick, even if you’re eating less, because those immune-related stress hormones keep pushing glucose levels up. Check your blood sugar more frequently than you normally would.
Certain combinations of symptoms call for emergency care. If you’re having trouble breathing or detect ketones in your urine (using over-the-counter test strips), go to the emergency room. The same applies if a fever persists and your blood sugar stays elevated despite your usual management routine. Persistent high blood sugar during illness can tip you toward DKA or HHS faster than you might expect, particularly if you’re dehydrated from the fever itself.
Why Blood Sugar Control Matters
The degree to which diabetes increases your infection and fever risk is closely tied to how well blood sugar is controlled. Every mechanism described above, from impaired white blood cell function to disrupted temperature regulation, worsens as blood sugar climbs. People in good glycemic control face meaningfully lower infection rates than those with chronically elevated levels. Keeping blood sugar in your target range won’t eliminate infection risk entirely, but it preserves more of your immune system’s normal function and keeps your body’s cooling mechanisms working closer to how they should.