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Taking medicines

It's important to take medicines safely and follow the instructions carefully. Get tips to make sure you are taking your medicines as you should.

Taking medicines at home is a common part of cancer treatment.

The medicines are much more likely to work if you take them as instructed. But we know from research that many people don’t take them as they should.

How you take a drug by mouth can affect how much of it is absorbed into your body. So if you don’t take it as you should, less of the drug may reach your cancer.

What affects how medicines work

There are a number of factors that affect how a drug is absorbed and how well it works.

Drugs stay active in the body for a particular length of time, from a couple of hours to over a day. This is why you need to take different drugs at different intervals of time.

The time it takes for the body to absorb a drug and be most effective also varies. 

Drugs must be taken at regular times to make sure you have the right level of the drug in your body. If you forget or miss a dose it can take some time to get back to the right level.

This is the same for drugs that control symptoms or that treat your cancer. For example, painkillers work best if you take them regularly so that the drug level is maintained in your body and so keeps pain under control.  Cancer drugs work in the same way, maintaining the cancer drug levels allows them to act on cancer cells more effectively.

Everyone forgets to take tablets sometimes. What you need to do if you forget a dose depends on the medicine you are taking. Missing one dose is unlikely to be a problem. But missing a dose a couple of times a day, or a week for a daily tablet, could mean the treatment doesn’t work as well as it should.

Tell your cancer doctor or specialist nurse if you have missed several doses in a row.

It is important to keep taking a drug for as long as your doctor has told you to. This could be weeks, months or even years.

For example, the hormone therapy tamoxifen for breast cancer is a tablet you take daily for 5 years. It reduces the risk of the cancer coming back.

The 5 year period was chosen after a lot of clinical research comparing how well the drug worked when taken for different numbers of years. A shorter time meant the cancer was more likely to come back. A longer time didn’t significantly help to lower the risk any further.

Treatment cycles

You take some cancer medicines in treatment cycles. This means that you take the drug for a set period of time, followed by a break, also for a fixed period of time. So, you might take a drug every day for a week and then not take it for 2 weeks. This 3 week period in total is one cycle of treatment.

It is important to remember to take the cancer medicines exactly as you have been told to. The break from treatment is important too. For many cancer drugs, it allows your body to recover.

For drugs to work, they must be broken down and absorbed into the body. When you take medicines by mouth as tablets, capsules or liquids, this process happens in the stomach or gut.

Some drugs are better absorbed on a full stomach and some on an empty stomach. If there are particular instructions about this your doctor, nurse or pharmacist will tell you. And it will be on the information sheet you get with your tablets.

Some foods affect how much of a drug you absorb, which could stop it from working as well as it should. For example, grapefruit interferes with a number of drugs. This information will be part of the instructions you get with your drugs.

Check with your doctor, nurse or pharmacist if you are not sure if you should take your drugs on an empty stomach or not.

Having diarrhoea or being sick might affect the amount of the drug that stays in your body. You might not be absorbing as much of it as you should.

Tell your cancer doctor or nurse if you have diarrhoea or are being sick. They need to know how your cancer treatment is being affected. And they will also be able to prescribe medicines to help.

Some drugs can affect each other, changing how much you absorb. Tell your doctor about any other medicines you are taking, including vitamins, and alternative or complementary therapies.

Supplements or therapies can interfere with how well medicines work. For example, St John’s Wort can affect the absorption of drugs. And laxatives can make a drug pass through your system more quickly.

Check with your cancer doctor, nurse or pharmacist before you take any medicines that you have bought yourself.

Like food, some drugs can go off. Some need to be kept in the fridge. Others need to be kept at room temperature. Follow any instructions about where and how you keep them.

You might be used to keeping medicines in the bathroom cabinet. But because the temperature varies a lot in bathrooms and the air may be damp, it is best not to keep medicines there.

All medicines have expiry dates. Always make sure any medicines you have are within the expiry date.

Problems with taking medicines correctly

There are many reasons why people don’t take medicines as they’ve been told to.

Understanding how to take your medicine

We know from research that people sometimes don’t understand exactly how to take medicines, or the instructions are too complicated. Ask your doctor, nurse or pharmacist to explain again. It might help to ask them to write it down.

It is also important to understand why you are taking a particular medicine and what it will mean if you don’t take it. If you don’t understand why you are taking a particular medicine you are less likely to carry on taking it.

Difficulty swallowing tablets or opening packets

You might have difficulty swallowing tablets, or can’t open the bottle. Let your doctor, nurse or pharmacist know. Some drugs are available as liquids or you can have them in a different type of container.

Side effects

Side effects of a drug might be too difficult to cope with, or it may taste horrible.

Side effects can often be controlled so let your doctor or nurse know if you have them. They can look at ways of helping you cope with any problems.


There are a number of things you can do to make sure you are taking your medicines as you should.

Finding out about your medicines

Find out why you are taking each drug. If you know what it’s for and how important it is, that will help you to remember.

You also need to know:

  • how should you store it
  • how long will you be taking it for
  • what the side effects are and who you can contact if you have any
  • what to do if you miss a dose

Make sure you know how you should take each drug including:

  • what time to take it
  • whether you can take it at the same time as other drugs
  • when to stop taking the drug
  • whether you need to take it with a full or empty stomach

We all forget to take medicines sometimes. It can help to write down when you need to take them, along with any instructions you need to follow.

Using a pill box

If you have several different tablets to take, a pill box can be helpful. These are divided into smaller boxes for each day of the week. There are compartments for different times of the day. 

You fill the box up once a week with your tablets. Or you can get someone to do it for you.

Setting an alarm

Setting an alarm on your watch, clock or mobile phone can help you remember to take your medicine. If you are taking more than one medicine a day you could make a chart with all your drugs and times listed. You could ask a helpful friend or relative to make one for you if you find it a bit daunting. 

Making a chart

You could make a chart to help you remember if you have taken your medicines. You can tick off the medicines as you take them.

Last reviewed: 
13 Apr 2016
  • Cohort study examining tamoxifen adherence and its relationship to mortality in women with breast cancer

    C McCowan and others

    British Journal of Cancer, 2008

    Volume 99, Issue 11

  • Medicines adherence: involving patients in decisions about prescribed medicines and supporting adherence

    National Institute for Health and Care Excellence, 2009

  • Medicines Optimisation: Helping patients to make the most of medicines. Good practice guidance for healthcare professionals in England

    Royal Pharmaceutical Society, 2013

  • Patient adherence and persistence with oral anticancer treatment

    K Ruddy, E Mayer and A Partridge

    CA: A Cancer Journal for Clinicians, 2009

    Volume 59, Issue 1

  • Polypharmacy in elderly patients with cancer: clinical implications and management

    J Lees and A Chan

    Lancet Oncology, 2011

    Volume 12, Issue 13

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