How Illness Can Affect Blood Sugar Levels and Diabetes Management
When you live with diabetes, getting sick can bring more challenges than just dealing with a cough, congestion, fever, or upset stomach. Even a common cold can affect blood glucose levels and make your usual diabetes management routine more difficult. Understanding how illness influences blood sugar can help you recognize changes, prepare for sick days, and know when to contact your healthcare provider.
Whether you use a continuous glucose monitor (CGM), an insulin pump, a blood glucose meter, or another diabetes management method, having a plan for days when you are not feeling well is an important part of staying prepared.
Why Illness Can Affect Blood Sugar
When your body fights an infection, it responds by releasing hormones that help it manage the physical stress of being sick. These stress hormones can cause the liver to release more glucose into the bloodstream and can make the body less responsive to insulin.
As a result, blood glucose levels may rise even when you are eating less than usual. This can happen with illnesses such as the common cold, influenza, respiratory infections, and other infections.
However, illness does not affect everyone the same way. Some people experience higher glucose levels, while others may develop low blood sugar, especially if they are eating less than usual while continuing certain diabetes medications. Vomiting, diarrhea, dehydration, and changes in activity can also make glucose levels less predictable.
This is why it is important not to assume that your blood sugar will behave as it normally does when you are sick. Monitoring your levels and following the sick day instructions provided by your healthcare team can help you respond to changes more safely.
How Common Symptoms Can Influence Glucose Levels
Different symptoms can affect diabetes management in different ways.
Fever and Infection
A fever can increase the body’s energy demands and contribute to changes in blood glucose. The infection causing the fever may also trigger a stress response that raises glucose levels.
Even if you are resting and eating less, your blood sugar may remain elevated. If you use a CGM, you may notice readings that differ from your usual patterns. These changes are worth monitoring, particularly if glucose remains high or you develop additional symptoms.
Nausea, Vomiting, and Diarrhea
Digestive symptoms can make it difficult to eat and drink normally. If you take insulin or other glucose lowering medications, reduced food intake may increase your risk of hypoglycemia, depending on your treatment plan.
Vomiting and diarrhea can also lead to dehydration, which may make blood glucose management more difficult. If you cannot keep fluids down, have repeated vomiting, or experience persistent diarrhea, contact your healthcare provider for guidance.
People with diabetes who use insulin should be especially careful not to stop insulin entirely without medical guidance. During illness, the body may still need insulin even when food intake is reduced.
Reduced Appetite
When you do not feel hungry, it may be tempting to skip meals. However, the effect of missing meals depends on the medications you take and your individual diabetes treatment plan.
Some medications can increase the risk of low blood sugar when you eat less than usual. Other treatments may require different adjustments during illness. Rather than changing medication doses on your own, follow your sick day plan or ask your healthcare provider what to do.
Dehydration
Fever, sweating, vomiting, diarrhea, and reduced fluid intake can all contribute to dehydration. High blood glucose can also increase fluid loss through urination.
Dehydration can become serious, particularly when glucose levels remain elevated or a person is unable to drink enough fluids. Unless you have been given fluid restrictions for another medical condition, take fluids regularly according to your healthcare team’s guidance.
The Role of Continuous Glucose Monitoring During Illness
Continuous glucose monitors provide information about glucose levels throughout the day and night. Instead of relying only on individual fingerstick readings, users can review their current readings and observe how glucose changes over time.
During illness, this information can help you recognize patterns that may otherwise be difficult to identify. For example, you might notice glucose levels rising over several hours, unexpected drops when you are eating less, or overnight changes that differ from your normal routine.
CGM trend information can be useful when discussing your symptoms and glucose patterns with your healthcare provider. Alerts, when enabled and configured appropriately, may also help you recognize readings that require attention.
It is important to remember that CGMs measure glucose in the fluid under the skin rather than directly in the blood. Readings can sometimes lag behind blood glucose changes, particularly when glucose is changing rapidly. If a reading does not match how you feel, or if your device instructions recommend confirmation, use a blood glucose meter and follow your device’s guidance.
A CGM does not replace a sick day plan or professional medical advice. It is a tool that can help you gather information and monitor trends while you follow your established care instructions.
Why Insulin Pump Users Should Pay Attention During Illness
Illness can present additional considerations for people who use insulin pumps. An insulin pump delivers insulin according to its programmed settings and the user’s treatment plan. If glucose levels rise unexpectedly, it is important to consider both the illness itself and whether insulin delivery is working as intended.
Illness related stress can increase insulin needs, but pump or infusion set problems can also cause glucose levels to rise. A kinked cannula, a dislodged infusion set, a leak, or an interruption in insulin delivery may prevent the expected amount of insulin from reaching the body.
People who use insulin pumps should follow their device instructions and diabetes team’s guidance for checking infusion sites, responding to persistent high glucose, checking ketones when directed, and using backup insulin if necessary.
Because many pump users rely on rapid acting insulin, an interruption in delivery can lead to ketone development more quickly than some people expect. Do not assume that a high reading during illness is caused only by the infection.
If glucose remains high despite following your prescribed correction plan, or you have elevated ketones, contact your healthcare team promptly. Follow your established emergency instructions if symptoms worsen.
What Is a Sick Day Plan?
A sick day plan is a set of instructions created with your healthcare team to help you manage diabetes when you are ill. It explains what to monitor, how to handle medication questions, when to check ketones if applicable, and when to seek medical care.
Your plan should be specific to your diabetes type, medications, devices, and other health conditions. Instructions for someone using an insulin pump may differ from those for someone taking oral medications or using multiple daily insulin injections.
A useful sick day plan addresses several important questions. How frequently should you check your glucose? Under what circumstances should you check ketones? What should you do if you cannot eat normally? Which medications may require special instructions during dehydration or illness? Who should you contact if your readings remain outside your target range?
Discuss these questions with your healthcare provider before you become sick. Having instructions available in advance can make it easier to respond when you are tired or uncomfortable.
Preparing for Sick Days Before They Happen
A little preparation can make diabetes management less stressful when illness occurs. Keep your glucose monitoring supplies available, make sure you have the supplies required for your diabetes devices, and check that you have access to your prescribed medications.
If you use a CGM or insulin pump, know how to respond if the device stops working or a sensor or infusion set needs attention. Keep the appropriate backup supplies available according to your healthcare team’s recommendations.
It can also help to keep a thermometer, fluids, and other basic illness supplies on hand. Make sure you know how to contact your healthcare provider after hours if you need advice.
Review your sick day plan periodically, especially if your medications, devices, or health conditions change. A plan that was appropriate several months ago may need to be updated.
When Should You Contact a Healthcare Provider?
Contact your healthcare provider if you are unsure how to manage your medications during illness, cannot maintain your usual fluid intake, have persistent vomiting or diarrhea, or experience glucose levels that remain outside the range specified in your sick day plan.
People with diabetes should also follow their clinician’s instructions about ketone testing, particularly during illness or when glucose levels are high. Ketones can be a warning sign of diabetic ketoacidosis (DKA), a serious condition that requires prompt treatment. DKA can sometimes occur even when glucose is not extremely elevated, particularly in people taking certain medications such as SGLT2 inhibitors.
Seek emergency medical attention if you experience difficulty breathing, confusion, fainting, severe weakness, severe abdominal pain, or signs of significant dehydration. Repeated vomiting, inability to keep fluids down, or high ketone levels may also require urgent evaluation. Do not delay emergency care while waiting for a glucose reading to change.
If you are taking an SGLT2 inhibitor and develop symptoms that could indicate DKA, such as nausea, vomiting, abdominal pain, or unusual breathing, seek urgent medical advice even if your glucose reading is not very high.
Stay Prepared for the Unexpected
Getting sick is part of life, but managing diabetes during illness does not have to mean navigating every change without a plan. Understanding how infections, appetite changes, dehydration, and stress can affect glucose levels helps you recognize when your usual routine may need extra attention.
Monitoring glucose, keeping your diabetes supplies accessible, and knowing when to contact your healthcare provider can help you respond more confidently when you are not feeling your best.
At Southeast Diabetes, we understand the importance of having access to the diabetes management supplies prescribed for your care. Planning ahead for your monitoring and diabetes device needs can help you stay prepared for everyday routines as well as unexpected sick days.