Acute illness can move glucose in either direction. Fever, infection, pain, and stress hormones often raise it. Reduced food intake, vomiting, diarrhea, or a mismatch between food and glucose-lowering treatment can push it down, and dehydration can concentrate glucose and impair kidney function, while insufficient insulin can allow ketones to rise. A diabetes sick-day plan anticipates these competing risks before judgment is clouded by fatigue or nausea.
The plan must be personal. Type of diabetes, pregnancy, and age all change the response. So do usual medicines, insulin delivery, and kidney function. So do prior ketoacidosis, ability to monitor, and access to help. General education can explain what belongs in the plan, but it cannot supply your insulin adjustment or say which medicine you should hold.
Why an ordinary illness can disrupt glucose#
During infection or other physiologic stress, hormones such as cortisol, catecholamines, glucagon, and growth hormone help mobilize fuel: the liver releases glucose, and tissues can become less responsive to insulin. If you are eating less, you may therefore see glucose rise rather than fall.
The opposite remains possible. Nausea, diarrhea, delayed meals, or inability to absorb food can lower available carbohydrate. Insulin and some other glucose-lowering medicines may continue to act, and older adults, children, people with kidney impairment, and anyone with a history of severe hypoglycemia may have less room for error.
Fluid loss links several problems. Fever, rapid breathing, vomiting, diarrhea, and glucose-driven urination can all reduce circulating volume. Dehydration can worsen hyperglycemia, reduce kidney clearance of medicines, and contribute to dizziness or acute kidney injury. A sick-day plan therefore coordinates glucose, ketones, and intake rather than chasing one reading. It coordinates urine output, symptoms, and medicines.
Ketoacidosis and hyperosmolar crisis are different emergencies#
Diabetic ketoacidosis develops when effective insulin is too low and the body breaks down fat rapidly, producing acidic ketones. It is most common in type 1 diabetes, but it can occur in type 2 diabetes, during pregnancy, with interrupted insulin delivery, or in association with SGLT2 inhibitors. Nausea, vomiting, and abdominal pain are warning signs. So are thirst, frequent urination, and deep or difficult breathing. So are fruity breath, drowsiness, and confusion.
An SGLT2 inhibitor can be associated with ketoacidosis when glucose is not dramatically elevated. That is one reason a sick-day plan may call for ketone assessment based on symptoms and circumstances, not glucose alone. It is also why medication-specific instructions belong in the plan before illness.
Hyperosmolar hyperglycemic state usually features profound hyperglycemia and dehydration with little or no major ketosis; it is more common in type 2 diabetes and can cause weakness, neurologic changes, and altered consciousness. Both conditions need urgent medical care. Home monitoring is meant to identify risk early, not to normalize dangerous symptoms without help.
What a written sick-day plan should contain#
A useful plan answers operational questions in plain language:
- Which glucose method should be used if a continuous sensor appears inconsistent with symptoms?
- Under what conditions should ketones be checked, and should the person use blood or urine testing?
- What result or symptom triggers a same-day call, an urgent visit, or emergency services?
- Which medicines continue, which may need a temporary pause, and what exact clinician-approved rules govern insulin?
- How should fluids and carbohydrate be maintained when usual meals are not possible?
- What should happen if a pump, infusion set, sensor, meter, or test strip fails?
- Who is the daytime contact, who covers after hours, and where should the person go if help is unavailable?
- How will a child, older adult, care partner, school, or workplace use the plan?
The plan should identify the person, diabetes type, and allergies. It should identify the medicine list, insulin delivery method, usual monitoring tools, and relevant medical conditions. It should be dated, stored where it can be found, and shared with anyone expected to help. A plan written years ago may no longer match current medicines or technology.
Monitoring is about direction and context#
During illness, one value is less informative than a series. The pattern can show whether glucose is rising, falling, or not responding as expected. Ketone trends can identify an increasing insulin deficit. Temperature, breathing, and alertness add clinical context. So do fluid intake, vomiting, diarrhea, and urine output.
The American Diabetes Association's 2026 Standards advise education and access to ketone measurement for people at risk of ketoacidosis. They also advise prompt help when oral hydration cannot be maintained, vomiting continues, glucose or ketones do not improve with insulin given under the established plan, mental status changes, or illness worsens.
The exact testing interval is individualized. A fixed schedule copied from a general website may be inappropriate for a young child, pregnancy, pump therapy, a frail adult, or a person who has never been told to check ketones. The written plan should state the interval and escalation threshold chosen by the care team.
Medicines need drug-specific instructions#
“Keep taking everything” and “stop all diabetes medicines” are both unsafe universal rules. Insulin is essential for people with type 1 diabetes. ADA 2026 states that people receiving intensive insulin therapy should not stop or hold basal insulin even if they are not eating. At the same time, illness may change insulin needs, and giving a generic correction formula without a person's clinical details would be unsafe.
Some noninsulin medicines need temporary-hold instructions under defined circumstances. Poor oral intake, dehydration, acute kidney injury risk, surgery, or severe illness may affect the safety of metformin, SGLT2 inhibitors, sulfonylureas, GLP-1 receptor agonists, and other drugs in different ways. Medicines for blood pressure, fluid balance, pain, or other conditions can also matter.
This is why the plan should name each medicine and state what to do. You should not infer a hold rule from a drug class list, and you should not restart a held medicine until the plan's recovery criteria are met or the treating team confirms it. If you have no medication instructions when illness begins, contact the prescriber, diabetes team, pharmacist, or urgent clinical service.
Fluids and carbohydrate have separate jobs#
Fluids replace losses and support circulation and kidney function. Carbohydrate can help prevent hypoglycemia or starvation ketosis when usual food is not tolerated, and some people need sugar-free fluids because glucose is high, while others need carbohydrate-containing fluids because glucose is falling or insulin must continue. The correct choice depends on monitoring and the established plan.
Small, repeated amounts may be easier to tolerate than a large drink. Persistent inability to keep any fluid down is not a problem to solve through repeated home experiments. It is an escalation sign. Heart failure, kidney disease, dialysis, pregnancy, and fluid restrictions require a specific hydration plan because generic advice to “drink plenty” may be unsafe.
Over-the-counter cold and stomach remedies also deserve review. Some contain sugar, alcohol, decongestants, nonsteroidal anti-inflammatory drugs, or ingredients that interact with other medicines. A pharmacist can help select a product that fits the person's medical conditions and current treatment.
Technology helps, but it can fail during illness#
Continuous glucose monitoring can reveal direction and alert to highs or lows. A sensor may lag behind blood glucose during rapid change, and compression, dehydration, adhesion problems, or device error can create confusing results; the sick-day kit should include the backup method specified by the care team.
Insulin pump users need a written response to unexplained high glucose or ketones because interruption of rapid-acting insulin delivery can lead to ketosis quickly. The plan may include checking the infusion site, tubing, reservoir, and device alerts, then using a backup delivery method if instructed. Those steps and any insulin amount must come from the individual's pump-failure plan.
Supplies expire. A kit should be checked periodically for working meters, batteries, and strips. The check covers ketone materials, glucagon if prescribed, and pump supplies. It covers charging cables and a current medicine list. CDC emergency-planning resources recommend keeping diabetes supplies together and rotating them before expiration.
When to call and when to seek emergency care#
A same-day call is appropriate when the plan's glucose or ketone thresholds are reached, fever or gastrointestinal symptoms persist, medicine instructions are unclear, a device fails, intake is poor, or the person is not improving. Earlier contact is sensible for pregnancy, very young children, or frailty. It is sensible for immune compromise, advanced kidney disease, or a history of rapid ketoacidosis.
Emergency evaluation is warranted for trouble breathing, confusion, fainting, severe drowsiness, seizure, ongoing vomiting with inability to hydrate, severe abdominal pain with ketosis risk, high or worsening ketones, or a marked clinical decline. If you cannot safely monitor or administer treatment, you need help rather than a more complicated home plan.
Related guides explain hypoglycemia, how diabetes is diagnosed, and diabetes and kidney health. The site's clinical-strengths overview places prevention and chronic-disease safety in a broader primary-care frame.
Build and rehearse the plan while well#
At a routine visit, ask for a written plan that fits your current medicines and monitoring tools. Walk through a realistic scenario: fever with rising glucose, vomiting with falling glucose, positive ketones, a failed pump, or an after-hours illness. Confirm who will answer and where urgent care is available.
Teach-back is useful. You or a care partner explain the plan in your own words and demonstrate the monitoring tools. Any uncertainty becomes visible before an emergency. Review the plan after a medicine change, pregnancy, or hospitalization. Review it after a severe low, ketoacidosis episode, new kidney or heart condition, or change in caregiving.
The aim is not perfect self-management during every infection. It is a clear route from early monitoring to timely support, with fewer dangerous delays and fewer improvised medication decisions.
References#
- ADA Standards of Care in Diabetes 2026: glycemic goals and hyperglycemic crises
- American Diabetes Association: planning for sick days
- American Diabetes Association: managing ketones
- CDC: diabetic ketoacidosis
- CDC: diabetes care during emergencies
For your own health, talk with your clinician.*
Questions and answers
Can illness raise glucose even if I am barely eating?
Yes. Stress hormones can increase liver glucose release and insulin resistance. Reduced intake can also cause low glucose, so monitoring and context matter more than appetite alone.
Should insulin be stopped when food intake stops?
People using intensive insulin therapy generally should not stop basal insulin because doing so can precipitate ketoacidosis. Exact adjustments must follow the person's clinician-approved plan, not a generic online formula.
Can ketoacidosis occur without very high glucose?
Yes. This can occur during pregnancy and with SGLT2 inhibitor use, among other settings. Symptoms, ketones, medicines, and clinical condition need consideration even when glucose is not strikingly high.
Which diabetes tablets or injections should be held during illness?
There is no safe universal list for every person and illness. The answer depends on the medicine, hydration, food intake, kidney function, and severity. Ask the treating team to put drug-specific instructions in writing.
What belongs in a diabetes sick-day kit?
Common items include current glucose and ketone supplies, backup device materials, prescribed rescue treatment, a current medicine list, contact numbers, and the written plan. The exact contents should match the person's diabetes technology and risks.