Can Infections Trigger High Blood Sugar In Diabetes? Yes, infections can raise blood glucose in people with diabetes, sometimes sharply. This happens because the body treats infection as a physical stress, releasing hormones and inflammatory signals that make insulin less effective and push the liver to release more glucose.

However, this rise in blood sugar does not mean someone has done anything wrong. Even people who usually manage diabetes well can see unexpected highs during a cold, flu, urinary tract infection, pneumonia, dental infection, skin infection, or COVID-19. Therefore, understanding why this happens and what to watch for can make sick days safer and less stressful.

Why infections can raise blood sugar in diabetes

When an infection starts, the immune system needs energy to respond. Therefore, the body releases stress hormones such as adrenaline, cortisol, glucagon, and growth hormone. These hormones help the body cope with illness, yet they also tell the liver to release extra glucose into the bloodstream.

At the same time, these hormones make insulin work less effectively. As a result, glucose may stay in the blood instead of moving into muscles and other tissues. This problem can affect people with type 1 diabetes, type 2 diabetes, gestational diabetes, and other forms of diabetes.

Additionally, inflammation itself can worsen insulin resistance. During infection, immune cells release chemical messengers called cytokines. These signals help fight germs, but they can also interfere with normal glucose control.

For example, someone may eat very little during the flu but still see blood sugar rise. This can feel confusing, but it makes sense physiologically. The body is making and releasing more glucose while insulin is either insufficient or less effective.

The stress response: helpful for survival, difficult for glucose control

The stress response exists to protect the body. During an infection, hormones prepare the body to fight, heal, and maintain blood pressure. However, in diabetes, this same response can push glucose levels above target.

Cortisol and adrenaline increase glucose production in the liver. Meanwhile, glucagon encourages the liver to break down stored glycogen and create new glucose. Therefore, blood sugar can climb even if meals are smaller than usual.

Growth hormone can also reduce insulin sensitivity. Although this effect may help preserve glucose for critical immune functions, it creates a problem for diabetes management. Insulin doses or diabetes medicines that worked on a normal day may not match the body’s needs during illness.

In practical terms, infection can change the rules temporarily. A usual breakfast, usual medication plan, and usual activity level may no longer produce usual readings. Because of this, sick-day monitoring matters.

Inflammation and insulin resistance during infection

Inflammation plays a central role in the link between infection and hyperglycemia. When the immune system detects bacteria, viruses, or fungi, it activates inflammatory pathways. Consequently, the body becomes more insulin resistant.

This insulin resistance can happen quickly. For example, a person with diabetes may notice higher readings before obvious symptoms such as fever, cough, burning urination, or skin redness appear. In some cases, unexplained high glucose can become an early clue that infection is developing.

Additionally, viral infections can strongly affect metabolism. Research shows that viral illness can increase insulin resistance as part of a coordinated immune response. This response may support immune cell activity, but it can also make glucose control unpredictable.

Chronic infections may cause a slower but persistent effect. Periodontal disease, for instance, can increase inflammatory cytokines and worsen insulin resistance over time. Therefore, infection control includes both urgent treatment and long-term prevention.

Why blood sugar may rise even when appetite is low

Many people expect blood sugar to fall when they eat less. However, illness often works differently. During infection, the liver may release extra glucose regardless of food intake because stress hormones signal the body to make fuel available.

This explains why someone with diabetes may skip a meal, sip only soup, and still see high readings. Additionally, fever, pain, poor sleep, and dehydration can all add to the glucose rise. The body is under strain, and glucose control reflects that strain.

Some over-the-counter cold and flu medicines may also affect blood sugar. For example, certain cough syrups contain sugar, and some decongestants may raise glucose or blood pressure in sensitive people. Therefore, checking labels and asking a pharmacist can help.

Importantly, reduced eating can still create risk for low blood sugar if insulin or certain medications continue without adjustment. Because sick days can cause both highs and lows, frequent monitoring gives the clearest picture.

Common infections that can trigger high blood sugar

Almost any significant infection can raise blood sugar in diabetes. However, some infections appear especially common in real life and clinical care. These include respiratory infections, urinary tract infections, skin infections, dental infections, and viral illnesses.

Respiratory infections often cause noticeable glucose spikes. Colds, influenza, bronchitis, pneumonia, and COVID-19 can increase inflammation, fever, and dehydration. Consequently, readings may rise for several days, especially when the illness is severe.

Urinary tract infections also commonly affect glucose control. A UTI may cause burning, urgency, pelvic discomfort, fever, or confusion in older adults. Additionally, high blood sugar can increase glucose in urine, which may encourage bacterial growth and create a cycle.

Skin, soft tissue, and foot infections need particular attention in diabetes. Redness, warmth, swelling, drainage, slow healing, or worsening pain can signal infection. Therefore, early treatment can protect both glucose control and tissue health.

Respiratory infections: colds, flu, pneumonia, and COVID-19

Respiratory infections can create a strong metabolic response. Even a common cold may raise glucose, while influenza and pneumonia can cause much higher readings. Additionally, coughing, poor sleep, fever, and reduced fluids may worsen insulin resistance.

Influenza can be especially challenging because symptoms often arrive suddenly. People may develop fever, body aches, chills, and exhaustion within hours. As a result, diabetes routines such as meals, movement, hydration, and medication timing may become harder to maintain.

Pneumonia raises concern because it can cause severe inflammation and reduced oxygen levels. Therefore, blood sugar may rise significantly, and dehydration may develop quickly. Older adults and people with long-standing diabetes may face higher risk of hospitalization.

COVID-19 deserves special mention because it can trigger severe insulin resistance in some people. It may also precipitate diabetic ketoacidosis or hyperosmolar hyperglycemic state. Consequently, people with diabetes should treat COVID-related glucose changes seriously and seek advice when readings stay high.

Urinary, skin, dental, and soft tissue infections

Urinary tract infections can raise blood sugar through inflammation, stress hormones, and sometimes fever. However, high glucose can also make UTIs more likely. This two-way relationship means prevention and early treatment both matter.

Skin and soft tissue infections may start small but progress quickly in diabetes. For example, a blister, cut, ingrown toenail, or insect bite can become infected. Additionally, reduced circulation or nerve damage may delay pain signals, especially in the feet.

Dental infections can also affect blood glucose. Gum disease and periodontal infection increase inflammatory signals that worsen insulin resistance. Therefore, regular dental care supports more than oral health. It can also support diabetes management.

Warning signs deserve prompt attention:

• Fever or chills
• Increasing redness, swelling, warmth, or pain
• Pus, drainage, or a bad smell from a wound
• Burning urination or frequent urination
• Tooth pain, gum swelling, or bleeding gums

How high can blood sugar go during infection?

The rise in blood sugar varies widely. Some people see mild increases, while others experience persistent readings far above their usual range. However, severe infections can trigger dangerous hyperglycemia, especially when dehydration develops.

In type 1 diabetes, infection can increase the risk of diabetic ketoacidosis. DKA occurs when the body lacks enough effective insulin and starts breaking down fat rapidly, producing ketones. Consequently, blood becomes acidic, and the condition can become life-threatening.

In type 2 diabetes, severe infection and dehydration can contribute to hyperosmolar hyperglycemic state. HHS involves extremely high glucose and severe dehydration, usually with little or no ketone buildup. It often develops more gradually than DKA, but it remains a medical emergency.

Because infections frequently trigger both DKA and HHS, clinicians often search for infection when someone presents with a hyperglycemic crisis. Therefore, persistent high readings during illness should never be ignored.

Warning signs of DKA and HHS during infection

Recognizing emergency signs can save lives. During infection, high blood sugar can escalate faster than expected. Therefore, people who use insulin, have a history of DKA, or feel very unwell should stay especially alert.

Possible DKA symptoms include nausea, vomiting, abdominal pain, fruity-smelling breath, rapid breathing, extreme thirst, frequent urination, and confusion. Additionally, moderate or large ketones in blood or urine raise concern and require prompt action.

Possible HHS symptoms include very high glucose, intense thirst, dry mouth, weakness, drowsiness, confusion, vision changes, and reduced urination. Because HHS often involves severe dehydration, older adults may decline quickly.

Seek urgent medical help if any of these occur:

• Persistent very high glucose despite correction steps
• Moderate or large ketones
• Repeated vomiting or inability to keep fluids down
• Trouble breathing, chest pain, confusion, or fainting
• Signs of sepsis, such as high fever, shaking chills, or extreme weakness

The two-way relationship between diabetes and infection

The connection between diabetes and infection moves in both directions. Infections can raise blood sugar, and high blood sugar can increase infection risk. Consequently, one problem can feed the other.

Higher glucose levels can affect immune function. For example, high blood sugar can reduce how well white blood cells respond to germs. Additionally, glucose-rich tissues and urine may create an environment that helps some microbes grow.

Poor long-term glycemic control also increases infection risk. Studies have linked higher HbA1c levels with more community-treated and hospital-treated infections in both type 1 and type 2 diabetes. Therefore, stable glucose management between illnesses can reduce vulnerability.

However, infection risk does not reflect personal failure. Many factors influence both diabetes and immunity, including age, circulation, kidney function, medications, vaccination status, and access to care. A practical plan can lower risk without blame.

Can infection reveal undiagnosed diabetes?

Sometimes, infection does more than raise glucose in someone already diagnosed. It can reveal diabetes that had not yet been recognized. For example, a person may seek care for an infection and learn that their blood sugar is very high.

In other cases, infection can precipitate diabetic ketoacidosis, leading to a new diagnosis of type 1 diabetes. Childhood viral infections have long interested researchers because some may contribute to autoimmune beta-cell damage in genetically susceptible people.

Severe infections may also worsen underlying metabolic dysfunction. COVID-19, for instance, has appeared alongside new hyperglycemia and new-onset diabetes in some reports. However, researchers continue to study how often infection truly causes diabetes versus uncovering existing risk.

Therefore, marked hyperglycemia during infection deserves follow-up after recovery. If glucose remains high, a clinician may recommend A1c testing, fasting glucose, or other evaluation to clarify whether diabetes or prediabetes is present.

Sick-day monitoring: what to check and why

Sick-day monitoring helps catch problems early. Because infection can raise glucose suddenly, many diabetes care plans recommend checking blood sugar more often during illness. People using continuous glucose monitors should also confirm unexpected readings with a fingerstick when needed.

Ketone testing matters for many people, especially those with type 1 diabetes or anyone advised by a clinician to check ketones. Additionally, people taking SGLT2 inhibitors should understand ketone risk, since ketoacidosis can sometimes occur with less dramatic glucose elevation.

Hydration status also matters. Fever, sweating, vomiting, and diarrhea can cause fluid loss. As dehydration worsens, blood sugar may concentrate and circulation may decline, which can further raise risk.

Useful sick-day checks may include:

• Blood glucose trends, not just single numbers
• Blood or urine ketones when appropriate
• Temperature and symptoms of infection
• Fluid intake and urine output
• Ability to eat, drink, and take medicines safely

Medication and insulin considerations during infection

Medication needs can change during infection. However, people should avoid stopping insulin without medical guidance. In many cases, the body needs more insulin during illness, not less, even when appetite drops.

People who use insulin may need correction doses or temporary adjustments based on their care plan. Therefore, having written sick-day instructions from a diabetes clinician can reduce uncertainty when illness begins.

Some non-insulin diabetes medicines may need temporary changes during dehydration, vomiting, diarrhea, kidney stress, or poor intake. For example, clinicians may give specific guidance about metformin, SGLT2 inhibitors, sulfonylureas, GLP-1 receptor agonists, or other medications depending on the situation.

Because individual advice varies, preparation is essential. Ask your healthcare team before you get sick about which medicines to continue, which to pause, when to call, and what glucose or ketone levels require urgent care.

Hydration and food choices when blood sugar is high

Hydration supports recovery and glucose control. During infection, fluids help replace losses from fever, sweating, vomiting, or diarrhea. Additionally, fluids can reduce the risk of dehydration-related glucose concentration.

Water often works well, but some situations require carbohydrates or electrolytes. If someone cannot eat solid food and takes insulin or medicines that can cause low blood sugar, carbohydrate-containing fluids may help prevent lows. However, very high glucose may require sugar-free fluids unless a care plan says otherwise.

Gentle foods can make sick days easier. Examples include broth, crackers, toast, rice, applesauce, yogurt, soup, or other foods that the person tolerates. The goal is not perfection but steady hydration, safer medication use, and enough energy to recover.

Call a clinician if vomiting prevents fluid intake, diarrhea persists, or signs of dehydration appear. For example, dizziness, very dark urine, dry mouth, fast heartbeat, or confusion can signal that home care is no longer enough.

Prevention: reducing infection risk when you have diabetes

Preventing infections can also help prevent infection-related hyperglycemia. Although no strategy removes all risk, several habits lower the chance of illness and support better outcomes when infections happen.

Vaccination plays an important role. Flu, COVID-19, pneumococcal, hepatitis B, shingles, and other vaccines may apply depending on age, health history, and local guidance. Therefore, discussing vaccination with a clinician can strengthen a diabetes care plan.

Daily skin and foot care can also prevent complications. Check feet for cuts, blisters, redness, swelling, or drainage. Additionally, keep skin clean and moisturized, avoid walking barefoot when possible, and seek help for wounds that do not improve.

Practical prevention steps include:

• Wash hands regularly
• Keep dental visits and treat gum disease early
• Manage glucose targets as safely as possible
• Treat UTIs, wounds, and respiratory infections promptly
• Build a sick-day kit with supplies, medications, and emergency contacts

When to contact your healthcare team

Timely communication can prevent complications. If blood sugar stays above your sick-day threshold, contact your healthcare team for advice. Your threshold may differ depending on your age, pregnancy status, medications, and diabetes type.

Additionally, call if infection symptoms worsen or do not improve. Fever, painful urination, shortness of breath, chest discomfort, spreading redness, severe sore throat, or a wound with drainage may require evaluation and treatment.

People at higher risk should act sooner. This includes children, older adults, pregnant people, people with kidney disease, people with type 1 diabetes, and anyone with a history of DKA or HHS. Moreover, those who live alone may need extra support during illness.

Before illness occurs, ask your clinician these questions:

• How often should I check glucose when sick?
• When should I check ketones?
• What readings mean I should call or seek urgent care?
• Which medicines should I pause if I cannot eat or drink?
• Do I need a written sick-day plan?

What this means for daily diabetes care

The question Can Infections Trigger High Blood Sugar In Diabetes? matters because it affects everyday decisions. A sudden high reading may not always come from food, missed activity, or stress at work. Sometimes, it reflects an immune response to infection.

Therefore, glucose patterns can provide useful clues. If readings rise unexpectedly and remain high, consider whether symptoms of infection are present. A sore throat, cough, urinary symptoms, tooth pain, skin changes, fever, or unusual fatigue may help explain the change.

At the same time, avoid self-blame. Diabetes management already requires constant effort, and infections add another layer of complexity. A compassionate approach focuses on checking, hydrating, following the sick-day plan, and seeking help when needed.

Ultimately, preparation turns a frightening situation into a manageable one. With supplies ready, instructions written down, and a clear plan for calling your care team, you can respond to infection-related hyperglycemia more confidently.

Conclusion

Infections can trigger high blood sugar in diabetes through stress hormones, inflammation, insulin resistance, increased liver glucose release, and dehydration. The effect can range from mild temporary spikes to serious emergencies such as DKA or HHS, especially during severe illness. If you live with diabetes, create a sick-day plan with your healthcare team, monitor more often during infections, and seek urgent help for persistent high glucose, ketones, dehydration, vomiting, confusion, or breathing trouble.

FAQs

What is type 2 diabetes?
Type 2 diabetes is a chronic metabolic condition characterized by insulin resistance and a relative insufficiency of insulin, leading to increased blood glucose levels.

How common is type 2 diabetes?
Type 2 diabetes accounts for approximately 90-95% of all diabetes cases, making it the most common variety.

Who is primarily affected by type 2 diabetes?
While traditionally associated with adults, there is a rising incidence of type 2 diabetes among younger populations, largely driven by increasing obesity rates.

What are the common symptoms of type 2 diabetes?
Common symptoms include heightened thirst, frequent urination, fatigue, and blurred vision.

What are the potential complications of unmanaged type 2 diabetes?
If left unmanaged, type 2 diabetes can lead to serious complications such as cardiovascular disease, nerve damage, kidney failure, and vision impairment.

How many people are affected by type 2 diabetes in the United States?
Over 38 million Americans are living with type 2 diabetes.

What are the projections for type 2 diabetes globally by 2050?
Projections indicate that approximately 853 million adults globally will be affected by 2050.

Why is understanding type 2 diabetes important?
Understanding the intricacies of type 2 diabetes is essential for effective management and prevention strategies, empowering patients to take control of their health.

What resources are available for individuals with type 2 diabetes?
The 30-Day Diabetes Reset program offers guidance and community support for individuals seeking to manage or prevent type 2 diabetes.