What Should People Do if They Miss a Dose of Their Medicine?

The following article was written by UK Medicines Information (UKMi) pharmacists for NHS health care professionals.

Background

Sometimes people forget to take their medication at the normal time. This causes a problem because missing a dose may make the medicine less effective, but taking subsequent doses too close together increases the risk of side effects.

It is very difficult to give general guidance on what to do in these situations. Each case needs to be looked at individually. However, this Medicines Q&A offers some general guidance, which may help people who occasionally forget or delay a dose. This guidance does not apply to patients who forget doses frequently.

Answer

The answer section from the original version of this article referred to U.K. health care practices. The rest of this article, except for the following paragraph, is directly from the U.K. article because the information is relevant to people in the U.S.

This paragraph was revised to make it applicable to U.S. patients. This was done because although in both the U.K. and U.S patients are given a Patient Information Leaflet (PIL) when they fill their prescription, the PILs in the U.K. are more reliable than the ones in the U.S. because the contents of the U.S. PILs are not regulated by the FDA. For a small subset of drugs, including no more than 300 of the thousands of different prescription drugs available in the U.S., the FDA does require more accurate and complete information leaflets called Medication Guides. These are approved by the FDA and they are much more likely to contain information on what to do if a dose is missed and other important information. For drugs not being dispensed with Medication Guides, the PILs may not necessarily have instructions about missed doses. If there is no information in your PIL about missed doses, contact the physician who wrote the prescription or a pharmacist for advice. This is particularly advisable if more than one day of treatment has been missed.

General Advice

There is no situation where the next dose should be doubled if one is missed. This could be harmful.

• If the dose is more than 2 hours late for medicines taken once or twice each day people should usually take the dose as soon as they remember as long as the next dose is not due within a few hours. People should then continue as normal. The definition of a “few hours” will vary with each situation. Seek further advice if you’re not sure what this means in the situation you are dealing with.
• If the dose is more than 2 hours late for medicines taken frequently throughout the day it is usually advised to omit the missed dose, wait until the next dose is due, then continue as normal. For example, this advice would apply to an antibiotic or painkiller taken four times per day.

Specific Medicines

• Epilepsy medicines: it is especially important for patients with epilepsy to take their anticonvulsant medicines regularly. Missing a dose could trigger a convulsion. Usually people should take their dose as soon as they remember unless the next dose is due within a few hours. People who miss doses should avoid activities where having a convulsion could be dangerous.
• Oral contraceptives: look in the manufacturer’s Patient Information Leaflet (PIL) supplied with the medicine or contact a pharmacist for advice.
• Warfarin: warfarin should be taken at the same time each day, usually in the evening. If a missed dose can be taken within three hours, it should be taken. If more than three hours has elapsed, the dose should not be taken. Subsequent doses should be taken at the usual time. If a dose is omitted (not taken) make a note in the warfarin booklet and remember to tell the doctor at the next blood test appointment. If you are worried contact the anticoagulant clinic or the patient’s doctor for advice on any increased monitoring requirements.
• Insulin: patients should follow the advice given by their [general practitioner] or diabetic clinic.
• Methotrexate once weekly: if a dose is missed, it can be taken as soon as it is remembered if this is within two days. However, if the dose has been missed for more than two days then a doctor should be contacted for advice.
• Immune therapy and cancer drugs: people must ask their doctor for advice on what to do if they miss a dose of transplant rejection or cancer medicine.

People who frequently forget doses should speak to a pharmacist. The pharmacist can advise how to change medication to a simpler regimen, give tips on ways to help remember, or recommend a compliance aid. These aids are boxes which allow medicines to be put into labelled compartments to remind people to take them at specific times of the day or days of the week. There are many different types, some of which are pocket-sized, but note that not all medicines are suitable for these devices.

Summary

• Patient Information Leaflets usually have advice on missed doses.
• People should be warned that if they take medicines at shorter intervals than usual, they may get more side effects. Never double the next dose if one is missed.
• For any oral medicine it is usually all right to take a dose up to 2 hours late.
• If the dose is more than 2 hours late, and for medicines taken once or twice each day people should usually take the dose as soon as they remember as long as the next dose is not due within a few hours. For medicines taken more frequently, the missed dose should be omitted.
• For missed doses of warfarin, insulin, contraceptives, epilepsy medicines, weekly methotrexate, cancer medicines or immunosuppressants see above.
• If more than one day of treatment has been missed then contact the [general practitioner] or a pharmacist for advice.
• People should speak to their pharmacist if they regularly forget doses.

Limitations

This is not intended as definitive guidance, but general advice based on the opinions of the authors and their advisers. It may not be applicable in all circumstances. Seek appropriate clinical advice if uncertain. It is very difficult to give general guidance on what to do in these situations. Each situation needs to be looked at individually. This Medicines Q&A does not cover the situation where a patient vomits their medication.