This is good:
https://www.diabetes.co.uk/insulin/insulin-overdosage.html
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TREATING AN OVERDOSE OF LONG-ACTING INSULIN
If you have given too high a dose of long-acting insulin, this could affect you for up to 24 hours.
How you prevent a hypo will depend on how big the overdose was. If the overdose was large, such as a double dose, take carbohydrate to raise your sugar levels and call your health team or out-of-hours service for advice.
If the overdose was smaller, such as up to 5 units too much, take more carbohydrate than usual and aim to keep your sugar levels higher than normal over the next 24 hours to prevent a hypo occurring.
Test regularly through the day and at
any time you think you may feel hypo.
Take plenty of carbohydrate before sleeping. It is better to wake up with higher sugar levels than risking a hypo overnight. Don’t risk going low. If you cannot be certain that hypos will be avoided, call your health team or out-of-hours service.'