low sugar with fever

Overview

Low sugar with fever means your blood sugar level drops too low while your body is fighting an infection that causes a fever. This can happen because a fever makes your body use energy faster, and you may also eat less or lose fluids. It is most common in people with diabetes, especially those who take insulin or certain diabetes tablets.

It is fairly common in people with diabetes who are unwell with a fever. In people without diabetes, it is less common but can still happen during a serious infection.

It mostly affects people with diabetes, especially those on insulin or certain diabetes medicines. It can also affect older adults, young children, and anyone with a long-term condition that makes blood sugar control harder.

Symptoms

Common symptoms

• Shaking or trembling
• Sweating more than usual
• Feeling very hungry
• Fast heartbeat
• Feeling weak or dizzy
• Headache
• Blurred vision

Symptoms in children

• Fussiness or irritability
• Sleepiness or low energy
• Pale or clammy skin
• Crying that is hard to comfort
• Refusing to eat or drink

Symptoms in older adults

• Confusion or disorientation
• Feeling very weak or unsteady on their feet
• Slurred speech that looks like a stroke
• Feeling unusually anxious or restless
• Falls or sudden clumsiness

Causes

Main causes

• The fever makes your body burn energy faster, using up glucose in the blood.
• You may eat less because you feel unwell, so your sugar intake drops.
• Diabetes medicines, especially insulin, may lower sugar more than needed when you are not eating normally.
• Dehydration from fever can affect how your body handles glucose.
• Infection can cause your body to release stress hormones that change sugar levels.

Risk factors

• Having diabetes and taking insulin or certain oral diabetes medicines
• Being over 65 years old
• Having kidney or liver disease
• Drinking alcohol while unwell
• Having had low sugar episodes before

When to see a doctor

See a doctor urgently if:

• If you have symptoms of low sugar and they do not improve within 10–15 minutes of eating or drinking sugar
• If you have repeated low sugar readings despite treatment
• If you cannot keep any food or drink down because of vomiting
• If the person with a fever becomes very confused, sleepy, or difficult to wake

Book a routine appointment if:

• If you have diabetes and you are unwell with a fever, contact your diabetes care team for advice on adjusting your medicine.
• If you need help creating a sick-day plan for managing your blood sugar.
• If you have frequent low sugar episodes even without being ill.

Diagnosis

A healthcare provider can check your blood sugar level with a simple finger-prick test or a blood test from a vein. They will also ask about your symptoms, fever, and any medicines you are taking.

Tests that may be done

• Finger-prick blood glucose test
• Blood test at a clinic or hospital to confirm the result
• Urine or blood tests to check for infection or dehydration

What to expect at your appointment

The doctor or nurse will ask about your symptoms and medical history, check your temperature, and test your blood sugar. They may also look for signs of infection. In an emergency, treatment can be given right away without waiting for blood test results.

Treatment

Treatment has two parts: first, quickly raise your blood sugar back to a safe level. Then, manage the fever and the underlying infection to prevent another drop. Your healthcare provider can help you adjust your diabetes medicines during the illness.

Self-care at home

• If you can swallow, eat or drink a quick-sugar food like a glucose drink, orange juice, or sugary soda — about 15 grams of carbohydrate as advised by your care team.
• Recheck your blood sugar after 15 minutes; if it is still low, take another quick-sugar serving.
• Once your sugar is safe, eat a longer-acting snack like crackers with peanut butter or a sandwich to keep it stable.
• Drink fluids often to stay hydrated, such as water or clear soup.
• Follow your sick-day plan from your diabetes team, including how often to check your sugar.

Medical treatments

In a hospital or clinic, low sugar may be treated with fluids that contain glucose given through a drip, or with a medication that quickly raises blood sugar. Your regular medicines for diabetes may be adjusted while you are unwell. Always follow your healthcare provider's advice about medication changes.

Living with this condition

When you have a fever, check your blood sugar more often than usual — for many people that means every 2 to 4 hours. Keep a record of your readings and any symptoms. Have a plan ready for sick days, including what to eat and drink and when to call for help.

Lifestyle tips

• Get plenty of rest to help your body fight the infection.
• Keep easy-to-eat foods and drinks nearby in case your appetite is low.
• Let someone you trust know that you are unwell and may need help.
• Keep your glucose meter and any glucose treatments within reach.
• Avoid alcohol while you have a fever, as it can make low sugar worse.

Diet and exercise

While you have a fever, skip intense exercise and focus on rest. Eat small, gentle meals like soup, toast, rice, or fruit when you can. If you cannot eat much, sip sweet drinks or use glucose gel as your care team suggests. This is not a time to restrict carbohydrates.

Mental health and emotional wellbeing

Having a low sugar episode can be frightening, especially when you are already unwell. It is normal to feel anxious or worried. Talk to your care team about these feelings. If you have diabetes, connecting with others who understand can be reassuring.

Prevention

You cannot always prevent low sugar with fever, but you can lower the risk by having a sick-day plan, checking your blood sugar regularly when ill, staying hydrated, and eating small amounts frequently if your appetite is poor. It also helps to treat the cause of the fever, like an infection, with medical care.

Vaccines

Staying up to date with recommended vaccines, such as the flu vaccine, can help reduce the chance of illnesses that cause fevers. Talk to your healthcare provider about which vaccines are right for you.

Screening programmes

If you have diabetes or another condition that affects blood sugar, regular blood sugar checks and routine medical reviews can help catch problems early and adjust your treatment plan.

Complications

If left untreated

• Severe low sugar can lead to seizures or a coma.
• It can cause permanent brain damage if the brain is starved of sugar for too long.
• It can lead to falls or accidents because of dizziness or fainting.
• If combined with a high fever, it can cause confusion and make it harder to recover from the infection.

Long-term outlook

With quick treatment and proper guidance from your healthcare team, most people recover fully from low sugar with fever. Managing the fever and adjusting your diabetes medicine during the illness can help prevent repeat episodes and keep you safe. Things can improve quickly once you get the right care.

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