Sick days: the plan you make while you're healthy

Every T1D eventually learns this one the hard way: you catch a cold, you can barely eat, and your glucose climbs anyway. It feels like the meter is broken. It isn't. Sick days run on different physics, and the time to learn them is a boring Tuesday, not 2 a.m. with a fever.

Why a cold raises glucose when you're barely eating

When your body fights an infection, it releases a squad of stress hormones: cortisol, adrenaline, glucagon, growth hormone. Their job is to make sure a body under attack has fuel, so they tell the liver to dump stored glucose and make tissues more resistant to insulin. In a working pancreas, extra insulin quietly covers all this. In yours, nobody's home to answer, so glucose rises even on an empty stomach.

Two details make this sneakier than it sounds. Insulin needs can start climbing a day or two before you feel sick, while the infection is still brewing, and they can stay high for days after you feel better. So an unexplained stubborn-high stretch is sometimes your first symptom, and "I'm better, why am I still high" is a normal final act.

Ketones: the sick-day vital sign

Ketones are what the body produces when it burns fat because it can't use glucose, which in T1D means insulin is too scarce. Illness is their favorite moment: stress hormones push glucose up, insulin falls behind, and ketones start building. Left alone, that road ends in DKA. This is why ketone checking is the sick-day habit, the way temperature checking is the flu habit.

When exactly to check, and which numbers mean what, is a genuinely messy question. The major published guidelines disagree with each other: one big diabetes association keys checking to one glucose number, another names a different one, and the leading pediatric guideline says to check during every illness regardless of glucose. Their emergency thresholds differ too. That disagreement is the strongest argument there is for a written plan from your own care team, with your numbers on it.

A few concepts that are the same everywhere:

Blood beats urine, when you can get it. Urine strips lag reality in both directions: they can read innocent while blood ketones are already climbing, and they can stay positive for a day after the danger has passed. Blood ketone meters read the ketone that actually matters in DKA and react faster, which is why guidelines prefer them, especially for pump users and small kids. Urine strips are still the affordable, everywhere-available fallback, and far better than not checking.

Opened bottles lie. Urine ketone strips degrade fast once the bottle is open, on the order of months and by some accounts weeks. The bottle that's been sitting in the cabinet since last winter may read negative no matter what. Check dates, note when you opened it, or buy foil-wrapped singles.

Nauseous, not eating, still needs insulin

Here's the trap that fills emergency rooms: you can't eat, so you skip insulin, because insulin is for food, right? Except your liver never stopped releasing glucose, the stress hormones are shoveling more, and without insulin the ketone factory opens. People have landed in DKA from skipping a single sick day of insulin. Not eating never means not needing insulin. What it changes is how much, and that's your care team's math, not this page's.

The eating problem has a low-tech answer: little and often. When a meal is impossible, published guidance across the board converges on small sips of something with sugar in it every few minutes, juice, flat regular soda, popsicles, sips of broth in between for salt and fluid. When glucose is running high instead, the same sipping continues with sugar-free fluids. Where exactly that switch happens is a number your care team gives you. Either way the goal is the same: fluid keeps coming in, and when glucose allows, a trickle of carbs keeps coming with it, so there's something for insulin to work against.

Medicine-cabinet questions worth asking early

A handful of ordinary medicines have opinions about glucose, which makes them worth a conversation before you need them, not while you're holding the box in a pharmacy aisle at 9 p.m.

Steroids (prednisone and friends) are the famous one: they can push glucose up hard for as long as the course lasts. Any prescriber offering you steroids should hear "I have type 1" first, and your diabetes team should hear about the steroids.

Decongestants like pseudoephedrine are flagged in published guidance as glucose raisers, though plenty of experienced T1Ds report no effect at all. Individual thing. Ask, then watch your own data.

Cough syrups and drops are often mostly sugar. Sugar-free versions of nearly everything exist, and pharmacists are genuinely good at finding them.

Plain painkillers mostly behave, with footnotes: acetaminophen can confuse some older CGM sensors (newer generations are mostly immune, know your device), and guidance flags high doses of ibuprofen or aspirin as able to nudge glucose down.

Anti-nausea medication is a prescription conversation to have while healthy. Having it on hand can be the difference between riding out a stomach bug at home and an ER trip, and your team knows the situations where it's the wrong tool.

If you take anything beyond insulin for your diabetes, add it to the ask-list: some add-on medications come with published stop-while-sick advice for exactly these situations, and that call belongs to your care team.

When it stops being a home game

Most sick days are miserable and fine. A few aren't, and the line between them is not subtle if you know what to look for. Go to the emergency room, or call emergency services, for any of these:

• Vomiting that keeps coming back, or fluids that will not stay down. Fluids are the whole ballgame; when they stop working, home care has ended.

• Ketones that stay high despite doing everything your sick-day plan says.

• Breathing changes: fast, deep, labored breathing, or breath that smells fruity. That's DKA knocking, and it does not wait politely.

• Confusion, unusual drowsiness, or trouble staying awake.

• Dehydration that's winning: dizziness, dark urine, a dry mouth that sips don't fix.

• A low that won't come up, or lows stacking on a stomach bug faster than you can treat them.

And the unofficial seventh flag: you're scared and not sure it counts. That counts. Nobody at an ER has ever been angry at a person with T1D for coming in with ketones and vomiting. The regret only ever runs the other direction.

Parents, one addition: kids dehydrate faster than adults, and the younger the kid, the shorter the fuse. Pediatric guidance draws every one of these lines earlier for small children, so make the call sooner than you would for yourself, and lean on your pediatric team's after-hours line without apology. It exists for exactly this.

Build the kit before you're sick

Nobody assembles a sick-day kit while vomiting. The whole game is played in advance: one box, everything in it, everyone in the house knows where. Here's the list, tickable now and printable for the fridge.

One more advance move: the emergency card covers the scenario where a bad low speaks for you. Two minutes to make, lives in a wallet.

The quiet win

A sick day with T1D is never going to be fun. But there's a real difference between a miserable day where you check ketones on schedule, sip your way through, and know exactly which symptoms would send you to the ER, and a frightening day where every decision is improvised. The first kind is bought cheap: one conversation with your care team, one printed sheet, one stocked box.

If you're new to all of this, the first weeks guide sorts out what matters right now versus later. Parents, the school-day handoff covers the version of this where the sick day starts in a classroom.