ADHD medication – effects and side effects

Written and professionally reviewed by Martin Bergholtz, doctor in specialist training in psychiatry
Last updated: September 2026

For many people, medical treatment of ADHD can reduce difficulties with attention, impulsivity and restlessness. The aim is not to change your personality or remove all challenges, but to reduce the core symptoms and make it easier to function in everyday life.

Effects and side effects vary from person to person. The treatment is therefore planned individually and followed continuously by a doctor with relevant experience in ADHD.

How does ADHD medication work?

ADHD is associated with, among other things, difficulties regulating attention, activity level and impulses. ADHD medication affects the neurotransmitters dopamine and noradrenaline, which play an important role in the brain's regulation of, among other things, concentration, motivation and action.

When the medication has the desired effect, the person may, for example, experience:

• Better ability to sustain attention
• Less distractibility
• Greater calm and less impulsivity
• Easier starting and finishing of tasks
• Better overview and planning
• Less mental noise or racing thoughts
• Better ability to use strategies in everyday life

Some notice a clear difference, while others experience a more subtle improvement. The effect should be assessed on the basis of overall functioning and not only on whether the person feels more focused.

What types of ADHD medication are there?

ADHD medication can broadly be divided into stimulant and non-stimulant medications. The choice depends, among other things, on symptoms, general health, any other psychiatric conditions, previous experience and the risk of side effects.

Methylphenidate

Methylphenidate is a stimulant and comes in both short-acting and longer-acting formulations. The differences between the products concern, among other things, how quickly the effect starts, how long it lasts and how the medication is released through the day.

Methylphenidate is often used as one of the first medical treatment options for ADHD.

Lisdexamfetamine and dexamfetamine

Lisdexamfetamine is a longer-acting stimulant that is converted to dexamfetamine in the body. Dexamfetamine is also available in a shorter-acting form.

This type of medication may be relevant if methylphenidate does not have sufficient effect, causes significant side effects or for other reasons is not considered the right choice.

Atomoxetine

Atomoxetine is not a stimulant. Its effect typically develops more gradually than with stimulant medication, and it may take several weeks before the effect can be properly assessed.

Atomoxetine may be considered, among other things, if stimulant treatment is not tolerated, does not have sufficient effect or is not considered appropriate.

Guanfacine

Guanfacine is also a non-stimulant medication. It is used mainly in children and young people and may be relevant in selected situations depending on age, symptom picture and previous treatment.

The specific choice and use of medication must always be based on a medical assessment.

How is ADHD medication started?

Before medical treatment begins, the doctor reviews the person's mental and physical health. The aim is to assess whether there are factors that affect the choice of medication or the need for special follow-up.

The initial assessment may include, among other things:

• Current ADHD symptoms and level of functioning
• Previous and current mental disorders
• Physical health and relevant medical history
• Other medication and possible interactions
• Sleep, appetite and any substance use
• Blood pressure, pulse, height and weight
• Any heart disease in the person or close family

An electrocardiogram, also called an ECG, is not normally necessary for everyone, but may be relevant with certain symptoms, risk factors or previous heart disease.

Gradual adjustment towards the right dose

Treatment usually starts with a low dose that is gradually adjusted. This process is called titration. Along the way, the doctor continuously assesses how the effect weighs against any side effects until the right dose has been found.

The right dose is individual. It cannot be determined from age, height, weight or the severity of ADHD symptoms alone. A higher dose is not necessarily more effective than a lower one either.

During the titration, the following are assessed, among other things:

• The effect on ADHD symptoms
• Functioning at work, in education and at home
• How long the effect lasts through the day
• Sleep and appetite
• Mood and emotional reactions
• Pulse and blood pressure
• Any side effects

It can help to note effects and side effects from day to day. This makes it easier to assess patterns and discuss them with the treating doctor.

When can you feel the effect?

With stimulant medication, an effect can often be felt on the same day the medication is taken. However, it can take longer to find the right medication, the appropriate dose and a formulation with a suitable duration of effect.

Non-stimulant medication typically works more gradually. Here it can take several weeks before a reasonable assessment of the effect can be made.

A single good or bad day is therefore rarely enough to conclude whether the treatment is working. Sleep, stress, the menstrual cycle, diet, caffeine, illness and everyday strain can also affect both symptoms and how the medication feels.

Common side effects of ADHD medication

Side effects depend on the medication, dose and individual sensitivity. Some experience few or temporary discomforts, while others need a lower dose or a different medication.

Possible side effects include, among other things:

• Reduced appetite
• Weight loss
• Headache
• Dry mouth
• Nausea or stomach discomfort
• Difficulty falling asleep
• Increased pulse or blood pressure
• Inner restlessness
• Irritability or mood swings
• Feeling tense or emotionally flat
• Tiredness when the effect wears off

Side effects should be assessed in relation to the time the medication is taken, the dose and the medication's effect profile. Irritability can, for example, occur while the medication is working or when the effect is wearing off.

If you experience new, pronounced or persistent side effects, you should contact the treating doctor. The dose or medication should not be changed on your own.

What if the medication does not work?

Lack of effect from one medication does not necessarily mean that medical treatment in general will not help. Both the effect and the side effects can differ between the various medications and formulations.

If the treatment is not working as intended, the doctor may consider, among other things:

• Whether the dose is appropriate
• Whether the medication works for long enough
• Whether the time of taking it should be adjusted
• Whether side effects are limiting the beneficial effect
• Whether another medication should be tried
• Whether sleep, stress or other conditions are affecting the symptoms
• Whether the diagnostic and clinical assessment should be revisited

The goal is not to continue medication at any cost. The effect must be meaningful and in reasonable proportion to any side effects.

ADHD medication with co-occurring autism, anxiety or depression

People with ADHD may also have autism, anxiety, depression or other psychiatric difficulties. This does not necessarily rule out medical treatment, but it can affect the choice of medication, titration and follow-up.

With co-occurring autism or other neuropsychiatric conditions, it may be relevant to increase the dose more slowly and monitor effects and side effects more closely. Symptoms such as restlessness, sleep problems or emotional reactions can have several possible causes and must therefore be assessed individually.

ADHD medication treats ADHD symptoms, but is not in itself a treatment for autism, anxiety or depression.

Can medication stand alone?

Medication can reduce ADHD symptoms, but does not automatically create structure, good work habits or an understanding of your own needs.

For many, treatment works best as part of a broader approach, which may include, for example:

• Psychoeducation about ADHD
• Strategies for planning and time management
• Adjusting the work or study environment
• Support for sleep and stable everyday routines
• Psychological treatment
• Treatment of co-occurring mental health difficulties
• Involving a partner or family, when relevant

Medication can make it easier to use these strategies, but does not necessarily replace them.

Follow-up of medical treatment

Once the right dose has been found, the treatment should continue to be followed regularly. The need for medication, the perceived effect and any side effects can change over time.

At follow-ups, the following are typically assessed:

• Whether the medication continues to reduce ADHD symptoms
• How the person is functioning in everyday life
• Whether there are side effects
• Pulse, blood pressure and weight
• Sleep and appetite
• Whether the dose or medication is still appropriate

It may also be relevant at intervals to consider whether the treatment is still necessary and has the desired overall effect.

Medical treatment of ADHD at Nordisk Psykiatri

At Nordisk Psykiatri we offer medical treatment and follow-up for adults with ADHD. The treatment is based on a medical assessment and planned individually, with a focus on effect, side effects and functioning in everyday life.

We emphasise a careful and systematic start with ongoing follow-up. When relevant, the medical treatment can be combined with psychoeducation and psychological treatment, creating a connection between medication, understanding and concrete strategies.

Also read: ADHD, anxiety and depression, ADHD symptoms in adults and the difference between a psychologist and a psychiatrist.

Frequently asked questions about ADHD medication

Does ADHD medication change your personality?

That is not the aim of the treatment. The right medication and dose should reduce ADHD symptoms without making the person feel alien, emotionally flat or markedly changed. Such experiences should be discussed with the treating doctor.

Do you have to take ADHD medication every day?

It depends on the medication and the individual treatment plan. Some medications must be used regularly to achieve a stable effect. Any breaks from medication should be agreed with the doctor.

How long do you have to take ADHD medication?

There is no single fixed treatment period. Treatment continues as long as it has a meaningful effect, is tolerated and is still considered relevant. The need should be reviewed regularly.

Can you get side effects after a dose change?

Yes. Side effects can appear or become more noticeable when the dose is changed, even if the person has previously tolerated the medication. The discomfort should be discussed with the treating doctor, especially if it is pronounced or persistent.

Can medication cure ADHD?

No. Medication does not cure ADHD, but it can reduce the core symptoms and improve functioning while the medication is working.

Which ADHD medication is best?

There is no single medication that is best for everyone. The choice depends on the individual's symptoms, health, needs, effect and side effects.

Sources

• Danish Health Authority (Sundhedsstyrelsen). National clinical guideline for the assessment and treatment of ADHD in adults. Read the guideline
• Danish Health Authority (Sundhedsstyrelsen). National clinical recommendation for non-pharmacological treatment of ADHD in adults. Read the recommendation
• National Institute for Health and Care Excellence. Attention deficit hyperactivity disorder: diagnosis and management (NG87). Read the NICE guideline