7-minute read

Key points

  • Most people tolerate ADHD medication well, and side effects are usually mild and often settle within a few weeks.
  • Simple changes, such as taking your medication with food and early in the day, can make a big difference.
  • Always tell us about side effects on your monitoring form, and consider reporting them through the Yellow Card scheme.

Starting ADHD medication can be a big step. You might be hopeful about what it could change, and unsure about what to expect. Is a headache normal? Why aren’t you hungry at lunchtime? Should you be worried that your heart feels faster?

This Medication Safety Week, we’re answering those questions. The theme of this year’s international campaign is “side effects: don’t ignore them, report them”.

 

Will I get side effects?

Not everyone does. Most people tolerate ADHD medication well, and many have no side effects at all.

When side effects do happen, they’re usually mild. They tend to appear in the first few weeks, or after a change in dose, and often settle as your body adjusts.

ADHD medicines work by increasing the levels of two chemical messengers in the brain, dopamine and noradrenaline. These also play a part in appetite, sleep and heart rate, which is why some people notice changes in these areas.

 

Common side effects and what helps

These side effects can affect more than 1 in 10 people. Exact figures vary between medicines, and the leaflet in your medicine box gives the figures for yours.

Reduced appetite

You might eat less, forget meals or lose weight.

  • Eat breakfast before you take your medication.
  • Plan meals and snacks, and set reminders to eat.
  • Have a meal in the evening, when your medication has worn off.
  • Keep an eye on your weight.

Difficulty sleeping

You might take longer to fall asleep, or wake during the night.

  • Take your medication as early in the day as you can, unless you’ve been told otherwise.
  • Avoid caffeine later in the day.
  • Keep to a regular bedtime routine.

Headaches

You might notice mild aches or pressure around your head.

  • Drink plenty of water and eat regular meals.
  • Note when your headaches happen, so you can share this on your monitoring form.

Dry mouth

You might feel thirsty, or have dry lips or a sticky mouth.

  • Sip water regularly through the day.
  • Chew sugar-free gum.
  • Keep up good oral hygiene.

 

Less common side effects

These can affect fewer than 1 in 10 people.

  • Feeling sick (nausea): Take your medication with food, or straight after eating, and stay hydrated.
  • Feeling anxious or restless: Keep to good sleep habits, and let us know if it gets worse.
  • Irritability or mood changes: Record these on your monitoring form, and let us know if they continue.
  • Dizziness: Stand up slowly and stay hydrated.
  • A faster heartbeat, or being aware of your heartbeat: This is usually mild and settles with rest. If you feel unwell, or it isn’t improving, call NHS 111.

 

Getting the timing right

When you take your medication can make a big difference to side effects, especially sleep.

Long-acting medication

  • Take it early in the morning, after breakfast, ideally before 9am.
  • If you forget a dose, don’t take it later in the afternoon. Wait until the next morning instead.

Short-acting medication

  • Try to take your tablets at the same times each day, leaving 4 hours between doses.
  • At the start of treatment, take your last dose before 4pm, until you know whether a later dose affects your sleep.

 

Choose a good day to start

Some people feel dizzy when they first start treatment. If you work, drive or use equipment that could put you at risk, consider starting on a day off, such as a weekend.

 

Things to avoid or take care with

  • Caffeine: Coffee, tea, cola and energy drinks can raise your heart rate and blood pressure, and may make you feel more jittery or anxious. Try decaffeinated options where you can.
  • Alcohol: Alcohol can interact with stimulant medication. If you drink, it’s safest to wait until your medication has worn off. UK guidelines advise drinking no more than 14 units a week, spread over three or more days, with some alcohol-free days.
  • Nicotine: Cigarettes, vapes and nicotine gum can raise heart rate and blood pressure for some people. Cutting down may help.
  • Cannabis and other illegal drugs: These can be dangerous with ADHD medication and should be avoided.
  • Over-the-counter medicines: Some cold remedies and painkillers contain caffeine or decongestants, which can interact with ADHD medication. Ask a pharmacist before you buy.

If you’re prescribed any new medicine, check with your consultant, GP or pharmacist that it’s safe to take with your ADHD medication.

 

Can I drive on ADHD medication?

In England, Scotland and Wales, it’s legal to drive after taking some prescribed medicines, including amphetamine-based medicines such as dexamfetamine, if you take them as advised by a healthcare professional and they don’t make you unfit to drive. It’s illegal to drive if any medicine impairs your driving.

If you feel dizzy, drowsy or unwell, don’t drive.

 

Why your monitoring forms matter

Your monitoring forms help your clinical team understand how well your medication is working, whether you’re having side effects, and whether your treatment needs to change.

This is also why we regularly check your blood pressure, heart rate and weight. A 2025 review of 102 clinical trials found that, on average, ADHD medications have only small effects on blood pressure and heart rate. But the researchers noted that some people may have bigger changes, and recommended regular checks for everyone taking ADHD medication.

Even small changes are worth mentioning, so please complete your forms as accurately as you can.

When to stop and get advice

Please follow the guidance your prescriber has given you. In general, if you’re taking a stimulant medication:

  • Stop taking it and let your prescriber know if side effects feel too hard to manage, such as feeling unusually agitated or anxious, or your heart rate feeling uncomfortably fast.
  • Stop taking it and get medical advice if your blood pressure is consistently above 140/90, your heart rate is consistently above 100 beats per minute, or you have chest pain, palpitations, dizziness or difficulty breathing.
  • Pause it and tell your prescriber if you’re unwell with an illness such as a cold, flu, a chest infection or COVID-19.
  • Tell us straight away if you become pregnant or are planning a pregnancy.
  • Tell us if you develop any new health problems, especially heart problems.

Some non-stimulant medicines, such as guanfacine, shouldn’t be stopped suddenly, as this can cause a rise in blood pressure. If you take a non-stimulant, speak to your prescriber before stopping.

If you think you’re having a medical emergency, call 999. If in doubt, call NHS 111 for urgent advice.

 

Report it: the Yellow Card scheme

As well as telling us, you can report suspected side effects to the Medicines and Healthcare products Regulatory Agency (MHRA) through the Yellow Card scheme. Reports help to keep medicines safe for everyone. You only need to suspect that a medicine caused a side effect, not prove it.

You can report:

  • Online at yellowcard.mhra.gov.uk.
  • Through the free Yellow Card app.
  • By phone on 0800 731 6789, weekdays from 9am to 5pm.

Got more questions?

Join our webinar, Medication Side Effects: Your Questions Answered, where our clinicians will answer your questions about ADHD medication.

 

Reviewed by:
Dr Sam Spavin, ADHD Clinical Lead, 28.10.26

 

References

  1. MHRA. #MedSafetyWeek. Accessed 24 October 2026.
  2. nidirect. How alcohol affects your health, reflecting the UK Chief Medical Officers’ low-risk drinking guidelines. Accessed 24 October 2026.
  3. GOV.UK. Drugs and driving: the law. Accessed 24 October 2026.
  4. Farhat L, Revet A, Cortese S, et al. Comparative cardiovascular safety of medications for attention-deficit/hyperactivity disorder in children, adolescents, and adults: a systematic review and network meta-analysis. The Lancet Psychiatry. 2025. Summary: University of Southampton.
  5. Zhang L, Li L, Andell P, et al. Attention-deficit/hyperactivity disorder medications and long-term risk of cardiovascular diseases. JAMA Psychiatry. 2024;81(2):178–187. Summary: Psychiatric Times.
  6. Frimley ICB / Surrey and Borders Partnership. Guanfacine in adult services: shared care protocol. Accessed 24 October 2026.
  7. GOV.UK. The Yellow Card scheme: guidance for healthcare professionals, patients and the public. Accessed 24 October 2026.