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About this tool
Work out how late a missed dose is, whether the half-interval rule points to taking it or skipping it, and when the next dose is due.
This helper applies the half-interval rule that most patient information leaflets print for a missed dose: take it as soon as you remember unless you are more than halfway to the next dose, in which case leave it out and carry on normally — and never take two together. Enter the time the dose was due, the time now and how often you take the medicine, and it shows how late you are, which side of the halfway point that falls on, how many scheduled doses have gone by, and when the next one is due. Medicine types with their own published missed-dose rules, such as contraceptive pills, anticoagulants, insulin and anti-epileptics, are flagged instead of being run through the general rule.
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Add your input to the workspace.
Adjust the options until the result looks right.
Copy or download the output and put it to work.
Turns 'nearly time for the next dose' into a specific number for your dosing interval.
Shows when more than one scheduled dose has been missed, which changes the conversation with a pharmacist.
Contraceptives, anticoagulants, insulin, seizure medicines and transplant drugs are routed to their own instructions.
The standard leaflet rule is to take it as soon as you remember, unless it is nearly time for the next dose — then skip the missed one and carry on with the normal schedule. Never take a double dose to catch up. Your own leaflet overrides this, and some medicines have different instructions entirely.
The usual cut-off is halfway to the next scheduled dose. For a twice-daily medicine taken every 12 hours that is about 6 hours late; for a three-times-a-day medicine every 8 hours it is about 4 hours; for a once-daily medicine it is about 12 hours.
No. Doubling up raises the peak blood level and is a common cause of side effects and overdose, and it is explicitly warned against on almost every leaflet. If you have already taken a double dose and feel unwell, contact a doctor, a pharmacist or your local poisons helpline immediately.
Contraceptive pills, warfarin and other anticoagulants, insulin and diabetes medicines, anti-epileptics, transplant immunosuppressants, HIV antiretrovirals and weekly bisphosphonates all have product-specific instructions that the general halfway rule does not cover. For these, follow the leaflet or contact the prescribing clinic the same day.