Blood sugar too low and blood sugar dangerously high look alike from the outside, need opposite treatments, and are both routinely mistaken for drunkenness.

What you can see, and which way it points

Mark only what you can actually observe. Each answer is weighed towards a low or towards a high, the two columns are added up in front of you, and the tool says which picture it fits — or says plainly that it does not separate them and gives you the rule for that case. Nothing is saved, nothing leaves the page, and this cannot diagnose anything.

The two pictures, side by side

The rule for when you cannot tell

• Treat it as a low. If somebody with diabetes is confused, drowsy or behaving strangely and you have no meter and no clear picture, give fast sugar — provided they can swallow safely. That is the standard advice everywhere, and it is not a compromise.
• Because the two errors are not the same size. Fifteen grams of glucose given to somebody whose blood sugar is already twenty does almost nothing to their situation over the next few hours, and the hospital treatment is unchanged. Fifteen grams withheld from somebody at two can mean a seizure, a night in intensive care, or worse. One error is recoverable and the other is not.
• The exception is the mouth. Nothing by mouth for anybody who is unresponsive, fitting, or cannot swallow safely — no gel, no drink, no glucose rubbed on the gums. That is what an injection of glucagon and an ambulance are for, and it is the one place where "give them something sweet" becomes dangerous.
• Then measure, if there is anything to measure with. A finger-prick glucose settles the question in seconds and a ketone strip settles the second question. If neither exists in the house, that is a thing to fix this week, and it is cheap.
• And say what you did. Whoever comes next needs to know what was given and when, because it changes how the next reading is interpreted.

What a low actually needs

1. Fifteen grams of fast carbohydrate. Four or five glucose tablets, a small glass of ordinary fruit juice or non-diet cola, a tube of glucose gel, or four teaspoons of sugar in water. Not chocolate, not biscuits, not a cereal bar: fat slows the sugar down and this is a race.
2. Wait fifteen minutes and check again. If there is a meter, use it. If not, judge by whether they are coming back. This is the step people skip, and it is the one that prevents the second collapse.
3. Repeat the fifteen grams if they are still low. Up to three times. If there is no improvement after that, or they are getting worse, ring for help.
4. Then eat something longer-lasting. A sandwich, a banana, the next meal if it is due. Fast sugar wears off in under an hour and the reason for the low has not gone anywhere.
5. Do not drive for at least three quarters of an hour after recovery, and not until a meter reads properly above five. Reaction times stay impaired after the numbers look normal.
6. Write down that it happened. Two hypos in a week, or any hypo that needed help from another person, is a reason to review the doses — not a reason to eat more.

The lows that come back

• Alcohol. It suppresses the liver's ability to release stored glucose, and the hypo often arrives hours later, in the night, long after the drinking. It is also the commonest reason a hypo is treated as drunkenness by everybody present, including the person themselves. Alcohol on the breath is not an explanation; it is a risk factor.
• Sulfonylureas — gliclazide, glimepiride, glipizide. These tablets keep working for many hours, so a hypo they caused will very often come back after the first treatment. Somebody who has had a significant hypo on one of these usually needs to be seen and observed, not fixed at the kitchen table and left.
• Long-acting insulin and stacked doses. A hypo in the small hours often means the background insulin or the previous correction was too much, and treating it without changing anything guarantees a repeat.
• Exercise, and the day after it. Muscles keep taking up glucose for hours afterwards, so the hypo can come at bedtime after an afternoon walk.
• Losing the warning signs. After many years, or many hypos, the shaking and sweating can stop happening — the first sign becomes confusion. That is a specific, important thing to tell a clinician, because it changes targets and it changes driving.
• Kidney trouble, weight loss and stopping steroids all lower insulin requirements, sometimes quickly. A dose that was right last month can be too much this month.

The high one, and the rules for being ill

• Never stop insulin because of not eating. This is the single most important sentence about being unwell with type 1 diabetes. Illness raises insulin requirements even when appetite disappears, and stopping it is a common route into ketoacidosis.
• Check more often, and check ketones. Glucose every two to four hours while unwell, and ketones whenever the glucose is high or the person feels ill. Ketone strips for a meter, or a urine dipstick, are the difference between guessing and knowing.
• Drink, in small amounts, often. Dehydration drives the whole process. Sugar-free fluids if the glucose is high, sugary ones if it is low and they can still swallow.
• The signs that mean hospital now: vomiting that will not stop, deep heavy breathing, breath that smells of pear drops or nail varnish, severe stomach pain, drowsiness, or ketones above about 3 — and any of these in a child.
• Ketones with a normal glucose are not reassuring. They can mean the body is running on fat because there is not enough insulin, and they can also mean simple starvation ketosis. Which of the two it is depends on the insulin, the illness and the drugs — and it is a phone call, not a guess.
• Type 2 diabetes is not exempt. Ketoacidosis is less common in type 2 but it happens, and there is a second emergency — a very high glucose with severe dehydration and no ketones — that develops over days in older people and is easily read as confusion or a urine infection.

The tablet that hides it

• SGLT2 inhibitors can cause ketoacidosis with a glucose that looks nearly normal. The drugs whose names end in -flozin lower blood glucose by making the kidneys throw it away in the urine, which means the usual alarm — a high reading — may never appear while ketones climb.
• It is uncommon and it is not rare enough to ignore, and it is most likely during exactly the situations where people stop paying attention: an illness with vomiting, a period of not eating, a crash diet, heavy drinking, dehydration, and the days around an operation.
• These drugs are now prescribed well beyond diabetes, for heart failure and to protect the kidneys, which means many people taking one do not think of themselves as having a diabetes emergency to know about.
• The words that change the conversation are “please check ketones”. If somebody on a -flozin is unwell, vomiting, breathing deeply or has abdominal pain, ketones need measuring whatever the glucose says, and the drug is usually paused while they are ill.
• Ask for sick-day rules in writing when it is started, including which tablets to pause during vomiting, diarrhoea or fever, and when to restart. It is a routine request and it is very often not offered.

The things that look like both

• Stroke. Weakness or drooping on one side, or sudden trouble speaking, is a stroke pathway measured in minutes — and a hypo can mimic it exactly, which is why glucose is checked first in every stroke assessment. If you cannot check it, treat the low and call anyway.
• Serious infection. A fever with shivering, a high heart rate, fast breathing or a rash changes the priority: sepsis and ketoacidosis often arrive together, and both need the same door.
• Head injury. Confusion after a fall or a blow to the head is its own pathway, urgently so on a blood thinner, and it is not resolved by sugar.
• Alcohol and drugs. The overlap is almost total, which is why "he has had a few" is the sentence that delays treatment most often. If the person has diabetes, the sugar gets checked first, every time.
• Anything at all in somebody who cannot say what is wrong. In an older person, or somebody with dementia, new confusion may be an infection, a bladder that is not emptying, or a medicine — and the glucose is still the two-second test that rules one big thing in or out.

What to have in the house, and what to say

1. Glucose tablets or gel where everybody can find them — not only in a bag that leaves the house. Fifteen grams, twice over.
2. A working meter with in-date strips, and ketone strips. Both, and check the expiry once a year. Ketone strips are the half of this that almost nobody has.
3. Glucagon, if it has been prescribed, and somebody who has been shown how. A kit nobody can use is a decoration; ten minutes with a nurse fixes that.
4. Sick-day rules on paper, on the fridge. Which drugs to pause, when to check ketones, which numbers mean ring, and which mean go in.
5. Something that says they have diabetes — a card, a bracelet, a phone lock screen. It is the difference between being treated and being assumed drunk.
6. A note of the last two lows. When, what caused it, and whether anybody else had to help. That is what a review is built on.

The drill: 16 decisions

Sixteen ordinary moments — a man asleep in a chair who will not wake properly, a woman with a normal glucose and pear-drop breath, a teenager told to stop insulin because she is not eating, a neighbour assumed to be drunk. Most have an instinctive answer that sounds sensible and is wrong. Pick your move; every answer explains why.

The card

Print it, put it on the fridge next to the glucose tablets, and fill in the numbers.

🖨️ Print the card