Treating a low without overtreating
Why the fix for a low is a small, measured amount and a wait, even though your brain is asking for the whole cupboard.
When your glucose drops below 4 mmol/L, you feel awful and your brain screams for sugar, so it’s completely normal to eat everything in reach. But the fix is a small, measured amount, then a wait. Overtreating is what sends you high an hour later.
- A hypo (glucose below 4 mmol/L) is treated with roughly 15 to 20g of fast-acting carbohydrate: sugar that hits your blood quickly, like glucose tablets or juice.
- Then you wait 10 to 15 minutes and recheck. The waiting is the hard part, and it’s the part that stops the rebound high.
- If you’re still below 4, treat again with the same amount, wait again, recheck again.
- Once you’re back above 4, some slower carbohydrate (a sandwich, a biscuit) can stop it dropping straight back.
- Treating a low sends your glucose up. Too much sends it up too far, so you end the hour high instead of steady.
A hypo turns off the part of you that measures
Overtreating isn’t a willpower problem. When your glucose is low, your brain is short of its main fuel, and it responds by making you feel frightened, shaky and desperate to eat. That feeling doesn’t switch off the moment the sugar hits your mouth. It switches off when the glucose actually reaches your blood, which takes about 10 to 15 minutes.
So there’s a gap: you’ve eaten enough, but you still feel terrible, so you eat more. And more. By the time you feel human again, you’ve had two or three times what you needed, and that surplus carries you up past normal and into a high.
Knowing this in advance is most of the fix. The awful feeling is not a signal to keep eating. It’s a signal that the sugar hasn’t arrived yet.
15g, wait, recheck, repeat
The usual shape people are taught is sometimes called the 15/15 rule: around 15 to 20g of fast-acting carbohydrate, then 15 minutes, then a recheck. Fast-acting means carbohydrate with nothing to slow it down, so no fat, no protein, no fibre getting in the way. Glucose tablets, a small glass of ordinary (not diet) fizzy drink or juice, or jelly babies all work.
Chocolate feels like the obvious choice, but the fat in it slows the sugar down, so it lifts you more slowly than you need in a hypo. It’s a poor rescue and an easy thing to overeat.
If you recheck at 15 minutes and you’re still below 4, you repeat: another 15 to 20g, another wait, another check. That’s the whole method. It feels slow when you’re shaking, which is exactly why it’s worth deciding on it before you need it.
This is about not sending yourself the other way
Treating a low moves your glucose up, which is the whole point. The problem is that it’s easy to send it too far up. Overtreat, and you spend the next hour or two high, then you or your insulin correct that, and some people bounce straight back down again. That up-down-up pattern is exhausting, and it’s exactly what measured treatment is trying to avoid.
There’s a second reason overtreating is easy: if there’s still rapid insulin working in your body from a recent dose (sometimes called insulin on board), that insulin is still pulling your glucose down while you treat. It can make the hypo feel bottomless, so you eat more to stay ahead of it. Extra carbohydrate is something you can manage yourself; insulin adjustments are worked out with your diabetes team. So the answer to a stubborn low is the same measured dose plus a recheck, not a bigger one, and if you keep landing in this spot, that’s a pattern to take to your team rather than solve with more sugar.
What changes how much you actually need
15 to 20g is a starting point, not a fixed law. If you’ve got rapid insulin still active, or you exercised earlier, or you drank last night, a hypo can be more stubborn and you may need a second round. That’s not you failing to treat it properly, it’s the situation needing more than one go. What stays constant is the shape: treat, wait, recheck, and only treat again after the recheck, not instead of it. Delayed lows hours after activity or alcohol are common, which is why the recheck matters as much as the treatment.
What measured treatment looks like
Examples, not instructions or doses.
You wake at 3am shaking and your meter reads 3.2 mmol/L. Everything in you wants the whole fridge. You have your set fast-acting carb instead, stay sitting up, and wait. At 3.15 you recheck: 4.6. You have a couple of biscuits so it doesn’t sag again, and you’re not fighting a high at 5am.
You treat a hypo, wait, recheck at 15 minutes, and you’re still 3.6. This is exactly the case the recheck exists for. You treat again with the same amount, wait again, and check again, rather than assuming the first round didn’t count and eating three times as much.
You went for a long walk this afternoon and you’re low now, in the evening. Your muscles are still restocking, so this low can be deeper and you might need a second round. You keep to the same measured amount each time and keep rechecking, because the drop can keep going.
Worth paying attention to
Questions that make an appointment useful
When it's urgent
If someone with type 1 becomes too confused to treat themselves, cannot swallow safely, has a seizure or loses consciousness, this is a severe hypo and a medical emergency. Do not put food or drink in their mouth. If a glucagon kit is available and someone knows how to use it, use it, and call 999. For a hypo you can treat yourself but that keeps returning or worries you, contact your diabetes team or NHS 111.