Flu season with diabetes: your sick-day plan (before you need it)
There's a reason the diabetes community talks about the flu the way it does. As Beyond Type 1 puts it, getting sick "gets tricky with diabetes" — the flu is "the more unruly cousin… who outstays his welcome and can cause serious havoc if left unchecked" (). It's not just feeling awful. It's feeling awful while your blood sugar does things it doesn't normally do.
The good news is that a sick day with diabetes is a solved problem — as long as you solve it before you're sick. The worst time to figure out your plan is at 2 a.m. with a fever and a blood sugar that won't come down. So this is the calm version, written while you feel fine: why illness moves your numbers, the rules that don't change, and the short list of things to have ready.
None of this is medical advice. It's the plan you make with your care team, laid out so it's easy to follow on a day when thinking is hard. Your doctor, your pharmacist, and your medication's label always win the tie.
First, why being sick raises your blood sugar (even when you can't eat)
This surprises people every time: you're barely eating, and your blood sugar climbs anyway. It's not you doing something wrong — it's biology.
When your body fights an infection, it releases stress hormones like adrenaline and cortisol. Those hormones tell your liver to pour extra glucose into your blood, and they "reduce the effectiveness of insulin" at the same time (). So you get a double hit: more sugar coming in, and your insulin working less well against it — which is why levels can rise even without a meal ().
That single fact reframes the whole day. Sick highs aren't a failure of willpower or carb counting. They're expected — which means they're something you plan for, not something you feel guilty about.
Why the flu is genuinely higher-stakes with diabetes
Not to scare you — to explain why the plan is worth making. People with diabetes are at higher risk of serious flu complications even when their diabetes is well managed. The numbers the CDC reports are blunt: about 30% of adults hospitalized with flu have diabetes, and people with diabetes are roughly six times more likely to be hospitalized and three times more likely to die from flu-related complications than people without it (, via the ).
Here's the encouraging half of the same page: flu vaccination has been associated with 79% fewer flu-related hospitalizations among people with diabetes (). That's the highest-leverage thing on this entire list, and it happens before flu season, not during it.
The flu shot: what kind, and when
Two practical details the community asks about every fall.
Which one: the injectable flu shot is the one recommended for people with diabetes — generally not the nasal-spray version (the live/LAIV vaccine) ( / ). When you book it, ask for the shot.
When: the American Diabetes Association recommends getting vaccinated in early fall, ideally by the end of October — and it takes about two weeks to take full effect, so earlier beats later (). Flu season starts ramping in September. If you miss October, it's still worth getting in November or December.
While you're there, ask your doctor whether the pneumococcal (pneumonia) vaccine makes sense for you too — it's commonly recommended alongside the flu shot for people with diabetes because of the higher pneumonia risk ().
The one rule people get wrong: keep taking your medication
This is the question that causes the most 2 a.m. anxiety, so let's answer it plainly. When you're sick, keep taking your diabetes medicines as usual — even if you're not eating much, even if you're vomiting. Kaiser Permanente's sick-day guidance is direct about it: "Take your diabetes medicines as usual," and if you can't because you're vomiting, that's the moment to "call your doctor" ().
The reasoning matters: because illness is raising your blood sugar behind the scenes, your body often needs its insulin more than usual on a sick day, not less. Skipping basal (long-acting) insulin because you're not eating is exactly how a bad day becomes an emergency — your body still needs that background insulin to keep ketones in check.
That said, "keep taking your meds" is not the same as "keep your doses the same." Some medications may need adjusting when you're sick, and that's a conversation for your care team — ideally one you have before flu season, so your plan already has the answer. Never change an insulin dose on a guess.
A small tool that quietly helps: don't lose track of doses
Fever and fog are the enemy of routine. When you feel terrible, it's genuinely easy to forget whether you took this morning's pills — or to take them twice. This is the one place a boring pill organizer earns its keep on a sick day: a filled weekly planner turns "wait, did I take it?" into a glance at today's slot.
The ($7.99) does exactly that job — seven days laid out so each day has its place, filled once a week when you're well, so an empty slot proves today's dose is done even when your head is pounding. It's the cheapest, lowest-effort piece of a sick-day plan, and it removes a whole category of mistake on the day you're least sharp. (We go deeper on dose routines in .)
Your sick-day rules, in order
Here's the protocol the sources agree on. Print it, screenshot it, tape it inside a cabinet — somewhere you'll find it while sick.
- Keep taking your medications. As above — don't skip, and call your doctor before changing anything ().
- Test more often. Check your blood sugar at least every 3 to 4 hours — more often, even overnight, if it's climbing fast (). The ADA's rule of thumb is every 4 hours for type 1, and at least four times a day for type 2 ().
- Check ketones when your sugar is high. Beyond Type 1's threshold: check for ketones if your blood sugar goes over 240 mg/dL, and "call your doctor if it shows any ketones" (). Ketones plus high sugar is the early-warning sign of DKA, and it's the line where a sick day stops being a wait-it-out situation.
- Keep fluids and some carbs going. Aim for about 50 grams of carbohydrate every 3 to 4 hours if you can (). A simpler version from Beyond Type 1: 8 ounces of water or clear broth every hour, and 15 grams of carbs every hour if you're running low (). If your sugar is high, reach for sugar-free fluids; if you can't eat or you're running low, that's when sugary drinks earn their place.
- Watch the medicine you take for the flu, too. Large doses of aspirin can lower blood sugar, decongestants can raise it, and acetaminophen (Tylenol) can throw off some continuous glucose monitor readings — so "always read your labels" and dose accordingly ().
When to stop managing and call for help
Most sick days you ride out at home. These are the lines where you don't. Call your doctor — or head for urgent/emergency care — if (, ):
- You're vomiting or have diarrhea for more than about 6 hours, or can't keep fluids down.
- You have any ketones, especially with high blood sugar.
- Your blood sugar stays above 240 mg/dL despite taking your medication.
- You have a fever that isn't improving after a couple of days.
- You can't take your medication because you keep vomiting it back up.
When in doubt, call. Your care team would far rather hear from you early than meet you in the ER. As Kaiser notes, minor illnesses in people with diabetes — especially children with type 1 — "can lead to very high blood sugar levels and possible emergencies" ().
Build your sick-day kit now (while you feel fine)
The single best move is to assemble the kit before flu season, so a sick day is a matter of following a plan, not shopping for one. Beyond Type 1's own list is a good template ():
- A written sick-day plan from your care team — how often to test, when to check ketones, when to call, and your doctor's after-hours contact.
- Ketone strips or a meter, and a thermometer — the two measurements that tell you whether to wait or act.
- Sick-day food and drink: clear broth, caffeine-free clear sodas or ginger ale, sugar-free popsicles, saltines, oatmeal, glucose gel or tabs, and low-calorie sports drinks for fluids and electrolytes.
- Your usual medications, stocked and organized — a filled so doses don't slip on a foggy day, plus fast-acting glucose for lows.
- A glucagon kit and the know-how for someone at home to use it.
One note on insulin storage while we're here: being sick doesn't change the temperature rules. Unopened insulin still belongs in the fridge at 36–46°F (2–8°C), and if you keep a backup pen in a cooled case like the or a , a sick week is a fine time to make sure it's stored right and not expired. That's the whole extent of the cold-storage angle here — the sick-day work is really about routine, testing, and fluids.
Frequently asked questions
Q: Should people with diabetes get a flu shot? Yes. The CDC recommends an annual flu shot for people with diabetes, and vaccination has been associated with 79% fewer flu-related hospitalizations in this group (). Get the injectable version — the nasal-spray (live) vaccine is generally not recommended for people with diabetes ().
Q: When is the best time to get the flu shot if I have diabetes? Early fall, ideally by the end of October, since it takes about two weeks to take full effect (). Flu season begins ramping in September, so earlier is better — but if you miss October, getting vaccinated in November or December still helps.
Q: Does the flu raise blood sugar? Yes — often even when you're not eating. Fighting an infection releases stress hormones (adrenaline and cortisol) that make your liver release extra glucose and reduce how well your insulin works, so blood sugar tends to run high when you're sick ().
Q: Should I still take my insulin if I'm sick and not eating? Generally yes — keep taking your diabetes medicines as usual, and don't skip basal (long-acting) insulin just because you're not eating, because illness usually raises your need for it (). If you can't keep your medication down because you're vomiting, call your doctor. Any dose changes should come from your care team, not a guess.
Q: What are the sick-day rules for diabetes? Keep taking your medications; test your blood sugar at least every 3–4 hours; check ketones if your sugar goes over 240 mg/dL; keep fluids and some carbohydrate going (about 50 g every 3–4 hours, or 8 oz of fluid and 15 g of carbs hourly if you're low); and call your doctor if you have ketones, can't keep fluids down, or your sugar stays high (, ).
Q: When should I check for ketones when I'm sick? Check for ketones any time your blood sugar is high — Beyond Type 1's threshold is over 240 mg/dL — and call your doctor if the test shows any ketones (). Ketones with high blood sugar are the early sign of diabetic ketoacidosis (DKA), which needs medical attention.
Q: When should I call my doctor or go to the ER when I'm sick with diabetes? Call if you're vomiting or have diarrhea for more than about 6 hours, can't keep fluids down, have any ketones, run a fever that isn't improving after a couple of days, or your blood sugar stays above 240 mg/dL despite your medication (). When in doubt, call — early is always better.
Sources
This guide cites public-health and clinical guidance current as of 2026. Your medication's label and your care team are the authoritative source for your situation, including any sick-day dose adjustments.
This information is general and educational. It is not a substitute for the advice of your prescribing physician or pharmacist, and it is not medical advice about your specific medication, dose, or sick-day adjustments. Make your sick-day plan with your care team, and when in doubt, call them.