The one rule that never bends
Whatever else changes when you are ill, you do not stop your insulin. Not the day you cannot eat, not the day you vomit everything, not the day your reading is normal.
Never stop basal insulin — even if you are eating nothing
Basal insulin is not there to cover food. It is there to stop your liver flooding your bloodstream with glucose and to stop your body burning fat for fuel and producing ketones. In type 1 diabetes, stopping basal because you have not eaten is the fastest route to ketoacidosis there is. If you skip a meal and your glucose is normal, you can reasonably skip that meal’s bolus — you never skip the basal.
Why being ill sends glucose up
It feels backwards. You are eating less than usual, sometimes nothing at all, and your readings climb anyway. The reason is hormonal, not dietary.
Infection and injury trigger a stress response — cortisol, adrenaline, growth hormone. Those hormones do two things at once: they tell the liver to release stored glucose, and they make your cells substantially more resistant to the insulin you take. So your glucose rises from the inside while your usual doses do less work than they normally would. It is entirely possible to need considerably more insulin on a day you eat nothing.
There is a less common opposite case worth knowing. A gastrointestinal illness with vomiting and diarrhoea, where nothing is being absorbed, can drive glucose downinstead. This is the situation that needs the most careful watching, because the instinct to reduce insulin collides with the rule about never stopping basal. That is a same-day phone call to your doctor, not a decision to make alone.
Check what is in the medicine you have been given
Steroids raise glucose sharply, and a short course for a chest infection or a bad throat is common. Many cough syrups and tonics are sugar-based. Tell whoever prescribes for you that you have diabetes and are on insulin, and ask specifically whether what you are taking affects glucose — a sugar-free formulation usually exists.
Testing more, not less
Your normal testing routine assumes a normal day. Illness needs roughly a check every two to three hours, including overnight if things are moving.
The point of the frequency is not the individual number — it is the direction. A reading of 220 that was 180 two hours ago is a different situation from a 220 that was 300. Ketone development tracks a rising, sustained high, and the earlier you see the trend the smaller the intervention needed to stop it.
Trust blood over CGM on a sick day
Dehydration, fever and some medicines can all reduce sensor accuracy, and a sick day is exactly when the readings matter most. Keep using your CGM for the arrows and the trend, and confirm the decisions that matter — corrections, and anything above 250 mg/dL — with a fingerstick.
Ketones — when to test and what the result means
Ketones are what your body produces when it burns fat because it cannot use glucose for fuel. Testing for them is the single most useful thing you can do on a sick day, and it is the test most people do not have strips for when they need it.
Glucose is above 250 mg/dL — certainly if it stays there across two checks. Also test if you are vomiting, if you have a fruity or acetone smell on your breath, if you have abdominal pain, or if you feel far worse than the reading seems to justify. Blood ketone meters are more reliable than urine strips, because urine reflects what your body was doing an hour or two ago rather than now.
| Blood ketones | Reading | What to do | Urgency |
|---|---|---|---|
| Normal | Below 0.6 mmol/L | Continue sick day routine, keep testing every 2–3 hours | Monitor |
| Slightly raised | 0.6–1.5 mmol/L | Correction insulin per your plan, fluids, retest in 1–2 hours. Call your doctor | Act now |
| High | 1.5–3.0 mmol/L | Risk of DKA. Contact your doctor immediately for dosing instructions | Urgent |
| Very high | Above 3.0 mmol/L | Go to hospital. This does not get managed at home | Emergency |
Do not treat ketones with more carbohydrate
There is a persistent belief that ketones mean you need to eat. What clears ketones is insulin and fluid — insulin so your cells can use glucose again, fluid to flush and rehydrate. Adding carbohydrate to a high glucose with ketones present makes the problem larger. Salty fluids and a correction dose, guided by your plan and your doctor, are the response.
Two caveats worth knowing. Ketones with a normal glucose are not automatically an emergency — they can simply mean you have not eaten much — though it still warrants testing both again and a call if they are rising. And certain medicines, aspirin among them, can produce false positives on some strips. Also note that home ketone testing does not diagnose DKA: that is a clinical diagnosis needing blood gases and pH. What your strips do is tell you when to stop managing it yourself.
Adjusting insulin — bolus, not basal
You will usually need more insulin while ill. Where that extra insulin goes matters, and the general principle is to add it as correction doses rather than by raising your basal.
The reason is timing. Illness-driven insulin resistance appears over a day or two and disappears as you recover, often quite abruptly. Extra basal is a blunt instrument that stays in your system for many hours — so when the resistance lifts, usually just as you start feeling better, that raised basal is still working and produces a serious low. Correction doses can be given, assessed and stopped as things change.
✓ Generally sensible
- Keeping basal exactly as prescribed
- Correcting highs with rapid insulin per your ratios
- Skipping a meal bolus if you eat nothing and are in range
- Taking a correction-only dose when high and not eating
- Expecting to need larger corrections than usual
- Calling your doctor before you improvise
✕ Where it goes wrong
- Stopping basal because you are not eating
- Raising basal to chase a two-day illness
- Stacking corrections every hour out of impatience
- Waiting for an appointment before acting on ketones
- Assuming a normal reading means you are fine
- Treating high ketones at home
Sick days are prime conditions for stacking
High readings that refuse to come down are frustrating, and the temptation to correct again after an hour is strong. Rapid insulin still takes three to four hours to finish. Give each correction time, note what you gave and when, and remember that a high that will not shift is a reason to call your doctor rather than to keep dosing.
If you use a pump and a high will not respond to corrections at all, suspect the delivery rather than the dose. A kinked cannula or a failed site delivers nothing, and pump users have no long-acting insulin in reserve — which is why ketones develop faster. Give a correction by pen or syringe, then change the set and site.
Fluids, salt, and what to eat
Dehydration is the accelerant. High glucose makes you pass more urine, which dehydrates you, which concentrates your blood glucose further, which makes you pass more urine. In a hot Indian summer with a fever on top, that loop closes quickly.
Sip continuously rather than drinking a lot occasionally, especially if you are nauseated. Small amounts frequently stay down better.
Water alone does not replace what vomiting and diarrhoea take. Salted lemon water, clear soup or thin dal water, ORS — check whether your ORS is sugared and count it.
Stick to sugar-free fluids — water, salted broth, plain tea. You do not need carbohydrate, you need volume.
Now you do want the carbohydrate: juice, sweetened nimbu paani, regular soft drink. Sipped in small measured amounts, tested between.
On food, the aim is light, easy to digest and easy to count. Khichdi, curd rice, plain dal and rice, upma, toast, banana, thin porridge. If solid food is not happening, take carbohydrate as liquid instead — the important thing is that you know roughly how many grams went in so your dosing has something to work from.
Vomiting changes the risk
Persistent vomiting is the sick day symptom that most reliably ends in hospital, for three reasons at once: you cannot keep fluids down, you cannot keep carbohydrate down, and vomiting is itself an early sign of ketoacidosis.
That last point is the one people miss. It is natural to assume the vomiting is the illness. But nausea and vomiting are also how DKA presents, so vomiting with a high glucose and ketones is not a stomach bug to wait out — it is a reason to test ketones immediately and to call your doctor the same day, not tomorrow.
Two or more episodes in a few hours — make the call
If you cannot keep fluids down for more than a few hours, you cannot rehydrate yourself at home, and intravenous fluids are the treatment. This is particularly urgent for children, where dehydration progresses much faster. Do not wait for the morning.
When to stop managing it at home
Home management has a clear boundary. Any one of these means hospital — not a phone call first, not waiting to see how the night goes.
Go to the emergency room
Any single one of these
- Repeated vomiting — unable to hold fluids down
- High ketones with high glucose — above roughly 3.0 mmol/L
- Drowsiness or confusion — difficult to rouse
- Breathlessness — or deep, sighing, rapid breathing
- Severe abdominal pain — with high glucose
- Fruity or acetone breath — a classic DKA sign
- Glucose that will not come down — despite repeated corrections
Call your doctor today
Have your log open when you call
- Any detectable ketones — even at the low end
- Glucose over 250 — persisting past two checks
- Nausea, vomiting or diarrhoea — from the first episode
- Illness lasting beyond a day — without clear improvement
- You have been prescribed steroids — doses will need reviewing
- You are unsure — genuinely a sufficient reason
Have this ready before you dial
Your last several glucose readings with times, your ketone results, every insulin dose you have taken today with times, what you have managed to eat and drink, your temperature, and any other medicine you have started. A doctor can give useful instructions from that in two minutes, and almost none from “I have been running high”.
The sick day box
The worst time to discover your ketone strips expired in March is at 2 a.m. with a fever. Assemble this while you are well and check it twice a year.
| Item | Why it is in the box | Priority |
|---|---|---|
| Ketone strips or meter | The one test you cannot improvise. Check the expiry — they date faster than you expect | Essential |
| Spare glucose strips | You will use several days’ worth in one day | Essential |
| Spare insulin, both types | Including a backup pen or syringes if you are a pump user | Essential |
| Hypo treatment | Glucose tablets or powder — lows happen on sick days too | Essential |
| Glucagon kit | In date, and someone in the house knows where it is | Important |
| ORS sachets | For rehydration; note whether yours contains sugar | Important |
| Thermometer | Fever is information, and doctors ask | Important |
| Sugar-free paracetamol | Agreed with your doctor in advance, so you are not choosing while ill | Useful |
| Long-life carbohydrate | Juice cartons, plain biscuits — for the days nobody can go out | Useful |
| The written plan, printed | Because a phone dies and a fevered brain does not remember thresholds | Essential |
Write the plan before you need it
Everything above is general. What you actually need is a page with your numbers on it, agreed with your own doctor, written down while you are well and thinking clearly.
Bring this to your next routine appointment and ask your doctor to fill it in with you. It takes about ten minutes and it is the difference between a manageable Tuesday and an admission.
The glucose above which you test ketones, the ketone level at which you call, and the level at which you go straight to hospital.
How much extra rapid insulin to give at each ketone level, how often, and the maximum before you must call instead of dosing again.
Written explicitly, in your doctor’s words, including what to do on a day you eat nothing at all.
Doctor, diabetes educator, nearest hospital with an emergency department, and 108. On paper, not only in a phone.
Print three copies
One at home where the family can find it, one at work, and — if the plan is for a child — one with the school. The person who most needs to read your sick day plan is frequently not you.
Stock the sick day box now, not at 2 a.m.
Ketone strips, glucose strips, lancets, meters and CGM sensors — the supplies that only matter on the days you cannot go out and buy them. Free pan-India shipping.
The bottom line
Never stop your basal. Test every two to three hours. Check ketones above 250. Correct with rapid insulin, not by raising basal. Drink steadily and replace salt. Call your doctor early rather than late, and go to hospital for repeated vomiting, high ketones, drowsiness or breathlessness. Most sick days are entirely manageable at home — provided you decided how, before you got ill.
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