Starting a New Medicine: What the First Month Is Really Like

Starting a new medication side effects are most likely in the first week or two, and many of them ease as your body gets used to the medicine. Some do not settle, and a few need urgent help the same day. Here is what the first month usually feels like, and when to tell someone.

The first few days on a new medicine

The first thing most people do is open the leaflet, and the first thing the leaflet does is list everything that has ever been reported. It is a legal document, not a prediction. Most people take a new medicine without any real trouble. But the first month is where things go wrong quietly, and almost nobody is told that in advance.

A study of 258 people newly started on a medicine for a long-term condition, recruited through community pharmacies in south east England, followed them up at ten days and four weeks. By day ten, 30% were already not taking the medicine as prescribed — just over half of that unintentional, the rest a deliberate decision to stop or cut down. Two thirds of those still taking it reported at least one problem, and 61% wanted more information than they had been given. (Barber and colleagues, Patients' problems with new medication for chronic conditions, Quality & Safety in Health Care, 2004.)

That is the pattern we see at the counter. People take a medicine for a week, feel queasy or headachey, decide it does not agree with them, put the box in a drawer and say nothing at the next appointment. Often the side effect was one that would have faded. Sometimes a different medicine would have suited perfectly. Either way, nobody found out.

Most of the first week is about building a habit before you have to think about it. A few things genuinely help:

• Pin the dose to something you already do daily — brushing your teeth, the kettle going on. An event is easier to remember than a time.
• Check whether it needs food or an empty stomach, and whether mornings or nights suit it better. Some medicines cause drowsiness; some keep people awake.
• Learn the missed-dose rule before you miss one. It differs by medicine, so the leaflet is the place to look. As a general principle, NHS advice on most medicines is to take a forgotten dose when you remember unless it is nearly time for the next, and never to double up. Some medicines are exceptions, which is why it is worth asking.
• Keep a simple note. Two lines a day on your phone: the date, and how you felt. It turns "I have not felt right since I started it" into something a prescriber can work with.

Starting a new medication side effects: which settle and which do not

This is the distinction that matters most, and the one nobody explains. Broadly, unwanted effects fall into three groups.

The ones that usually settle. Many common early effects are your body adjusting rather than a sign of harm: mild nausea, headache, feeling woolly or drowsy, looser stools, a dry mouth, light-headedness on standing up. NHS guidance on antidepressants puts it plainly — many side effects ease after a couple of weeks as the body gets used to the medicine, though some carry on. That is broadly true across many medicine classes, and knowing it in advance is, in our experience, the single biggest reason people stay on a medicine long enough to find out whether it works.

The ones that do not settle, and need a change rather than patience. Some effects are built into how the medicine works, and waiting will not help. A dry, tickly cough with certain blood pressure medicines is the classic example: it can start weeks in and it does not fade. Constipation with strong painkillers needs managing, not enduring. Persistent dizziness, or anything clearly stopping you working, sleeping or eating, belongs here too. None of this means you must come off the medicine, or that you must stay on it. It means there is a conversation to be had, and often a simple answer: a different time of day, a different dose, a different medicine in the same family.

The ones that need help now. A small number of reactions are serious from the outset and have nothing to do with tolerance. Those are in the next section, and they are worth reading before you need them.

So how do you tell the first group from the second while it is happening? Over a fortnight, ask three things. Is it getting better week on week, or worse? Is it tolerable, or changing what you can do in a day? And did it start with the medicine? Your daily note answers all three.

What this article cannot do is tell you whether to carry on, stop or change your dose. That is not evasion: it depends on which medicine, why you are on it and what else you take. That decision belongs with a pharmacist, your GP or NHS 111, with your record in front of them.

When to speak to someone, and how urgently

Most side effects are a conversation, not an emergency. A few are an emergency, and they are easy to miss if you are telling yourself not to make a fuss. Use the table below: the top rows mean stop reading and ring 999.

If you are unsure which row you are in, that uncertainty is itself a reason to ring NHS 111, which is there for urgent problems that are not life-threatening and answers around the clock. Nobody will think you have wasted their time. Whether you call or come in to us, have the box with you, and be ready to say when you started it, when the symptom started and what else you take.

Our pharmacists also check whether the symptom is the medicine at all. A new medicine is a tempting explanation for anything in the same fortnight, and sometimes the wrong one. If what you have is an infection rather than a side effect, our Pharmacy First service may be able to assess and treat it there and then.

Reporting a side effect through the Yellow Card scheme

Alongside getting help, there is a second thing you can do, and most people have never heard of it. The Yellow Card scheme, run by the Medicines and Healthcare products Regulatory Agency, collects reports of suspected side effects so problems are spotted across the country rather than one patient at a time.

The part that surprises people: you do not have to be a doctor, nurse or pharmacist to report. Anyone can. Patients report their own side effects, parents report for a child, carers report for the person they look after. You can report a suspected problem with a medicine, a vaccine, a medical device, a blood product or an e-cigarette, on the Yellow Card website or through the Yellow Card app.

A few things worth knowing before you fill one in:

• You do not need to be certain the medicine caused it. The scheme asks for suspected reactions. Working out cause and effect is the regulator's job, not yours.
• It is not a complaint, and not about blaming a prescriber. Patterns in these reports are how leaflet warnings and dosing advice get changed.
• Effects not listed in the leaflet are especially worth reporting. A medicine is tested on a few thousand people and then used by millions, so rare reactions only appear once it is in use.
• It does not replace getting help. A report goes to the MHRA, not your GP, and nobody rings you back about your symptoms. Get medical advice first, report afterwards.

Have the box and leaflet in front of you, because the form asks for the medicine name, the batch number if you have it, and the dates. If you would rather not do it alone, bring it all in and our pharmacist will go through it with you.

When a medicine needs time to work

The other reason people give up in the first month has nothing to do with side effects. It is the quiet conclusion that the medicine is not doing anything.

Plenty of medicines produce no sensation at all, by design. A blood pressure medicine works perfectly while you feel exactly as you did before, because high blood pressure had no feeling attached to it either. Cholesterol and bone-strengthening medicines are the same: they change your risk over years, measured on a blood test or a scan, not how your Tuesday feels.

Others do produce a noticeable effect, but slowly. NHS guidance on antidepressants is that they usually take one to two weeks to start having an effect and up to eight weeks to work fully. Someone who stops at two weeks because they feel no better has often had the worst of the early side effects for nothing. Medicines for nerve pain and preventer inhalers for asthma build up in the same way.

There is also a group where the first prescription is deliberately a starting point: the dose is meant to be adjusted, or a blood test decides what happens next. If nobody told you that, it can look like the medicine failing when it is the plan working.

So the useful question when you are handed something new is not "will I feel better" but "how will we know if this is working, and when do we check?" It might be a blood pressure reading in six weeks, a blood test in three months, or whether stairs are easier. Ask for the checkpoint. If none was set, that is worth raising at a review — our post on what a medication review involves explains the different NHS reviews and how to ask for the right one. You can also read up on your own medicine on the NHS Medicines A to Z, which is plainer than the leaflet manages.

Help from your pharmacist in the first month

You do not need to be in trouble to ask. The most common conversation we have about new medicines takes two minutes at the counter and ends with someone relieved that what they are feeling is ordinary and expected.

If your new medicine is for a long-term condition, you may qualify for the New Medicine Service, which is free on the NHS and gives you a set of follow-up conversations with a pharmacist across roughly your first month. Our New Medicine Service page sets out which conditions are covered and how to start.

If your medicine does not qualify, nothing is lost. Asking a pharmacist about a medicine costs nothing and needs no appointment, whether the prescription came from us or not. Bring the box. We can tell you which effects are expected in the first fortnight, which usually fade, which are worth a same-day call, whether something you bought at the chemist is safe alongside it, and what to do about the dose you missed on Saturday. Our superintendent pharmacist, Poonam Pankhania, is an independent prescriber, and with your consent we can flag a problem to your GP practice rather than leaving you to chase it.

We have a private consultation room, so none of this has to happen in front of a queue. Many of the people we see about a new medicine walk down from North Harrow or come along the road from Rayners Lane, and others collect on their way home through Harrow town centre. If your repeats already come to us, we can see the rest of your medicine history, which makes these conversations quicker and safer.

You will find us at 160 Pinner Road, Harrow HA1 4JJ, open Monday to Friday from 9am to 6pm and Saturday from 9am to 1pm, closed on Sunday. Call 020 8863 6338 and ask for the pharmacist. If something feels seriously wrong right now, do not wait for us to open — ring 111, or 999 if it is one of the emergency signs in the table above.