Side effects of a double dose of blood pressure medication

If this has just happened

Call emergency services now if the person has fainted, is confused, has chest pain, is struggling to breathe, or has a very slow or irregular pulse.
Call for advice straight away if a child has swallowed any blood pressure medicine, or if an adult has taken much more than one extra dose.
In the United States, Poison Help is free and open all day on 1-800-222-1222. In the United Kingdom, call NHS 111. In Pakistan, call Rescue 1122 where it operates, or go to the nearest hospital emergency department. Elsewhere, call your pharmacist, doctor or local emergency number.
Do not take another dose, and do not try to make yourself sick.

Taking a blood pressure tablet twice by mistake is one of the most common medicine errors. For most adults, one accidental extra dose causes no symptoms or only mild ones, such as feeling lightheaded for a few hours. That is not true for everyone. The effect depends on which medicine it was, the strength, whether it is a slow-release form, and the person's age and health.

This guide explains the side effects to watch for, how they differ between types of blood pressure medicine, and what to do. It is general information and cannot tell you what is safe for you. A pharmacist, doctor or poison centre can, usually in a short phone call.

What a double dose does in the body

Blood pressure medicines work by relaxing blood vessels, slowing the heart, or removing salt and water. A double dose can push these effects further than intended. The main result is blood pressure that falls too low, known as hypotension. When pressure is too low, less blood reaches the brain, and the person feels dizzy or faint.

Studies of regular dosing show that doubling the dose of a blood pressure medicine usually lowers pressure only a little more than the standard dose. This is part of the reason a single extra tablet is often mild in an otherwise healthy adult. It is an average, and some drugs and some people do not follow it.

Common side effects of an extra dose

dizziness or lightheadedness, worse on standing up
feeling weak, tired or washed out
headache
nausea
blurred vision
a pulse that is slower or faster than usual
passing more urine than normal, with water tablets

Symptoms often begin within 30 to 60 minutes of the extra dose. With slow-release and long-acting tablets they can start later and last many hours, sometimes into the next day.

Warning signs that need urgent help

fainting or nearly fainting
confusion, unusual drowsiness or difficulty waking
chest pain or tightness
shortness of breath or wheezing
a very slow pulse, especially under 50 beats a minute with symptoms
cold, clammy or pale skin
a home reading with the top number under 90, together with symptoms

Side effects by type of blood pressure medicine

Type	Examples	What an extra dose may cause	Points to know
ACE inhibitors	Lisinopril, ramipril, enalapril	Low blood pressure, dizziness	A single extra dose is usually tolerated well by adults. Repeated high doses can affect the kidneys and raise potassium.
ARBs	Losartan, valsartan, candesartan	Low blood pressure, dizziness	Similar to ACE inhibitors
Calcium channel blockers, amlodipine type	Amlodipine, nifedipine, felodipine	Low blood pressure, flushing, headache, fast pulse, swollen ankles	Amlodipine is long-acting, so effects can last more than a day
Calcium channel blockers, heart-slowing type	Verapamil, diltiazem	Slow pulse, low blood pressure, tiredness	More dangerous in overdose than most other types. Always ask for advice.
Beta blockers	Metoprolol, bisoprolol, atenolol, propranolol	Slow pulse, low blood pressure, tiredness, cold hands, wheeze in people with asthma	Can mask or cause low blood sugar, especially in people with diabetes and in children
Diuretics (water tablets)	Hydrochlorothiazide, indapamide, furosemide	More urine, thirst, dizziness, muscle cramps	The main risk is losing too much fluid and salt
Alpha blockers	Doxazosin, prazosin	Marked dizziness on standing, fainting	Sit or lie down and rise slowly
Centrally acting medicines	Clonidine, methyldopa	Drowsiness, slow pulse, low blood pressure, dry mouth	Clonidine is especially dangerous for children, even in small amounts

Many people take a combination tablet that contains two of these types. Check the box or leaflet so that you can tell the adviser exactly what was taken.

Who is more likely to have problems

Older adults, who are more sensitive to low blood pressure and more likely to be hurt in a fall.
People who take several blood pressure medicines, or other medicines that lower pressure.
People with kidney disease, heart failure or a slow heart rhythm.
Anyone who is dehydrated, for example after vomiting, diarrhoea, heavy sweating or fasting in hot weather.
People who have drunk alcohol, which lowers blood pressure further.
Children. A single adult tablet of some blood pressure medicines can seriously harm a small child. Treat any accidental swallowing by a child as an emergency.

What to do, step by step

Stay calm and stop what you are doing. Do not drive, climb ladders or operate machinery.
Work out what was taken. Note the name, the strength in milligrams, how many tablets and at what time. Keep the packaging beside you.
Call for advice. A poison centre, pharmacist or doctor can tell you whether you can stay at home and what to watch for. Have the packaging and a list of your other medicines ready.
Sit or lie down if you feel lightheaded. Raising your legs helps blood return to the brain. Get up slowly.
Drink water normally unless you have been told to limit fluids.
Check your blood pressure and pulse if you have a home monitor, and write the readings down with the time.
Ask someone to stay with you for the next few hours if you can.
Ask about your next dose. Advice differs by medicine. Often you will be told to skip the next dose or to return to your usual schedule the following day. Do not decide this by guessing.

What not to do

Do not take anything to "cancel out" the extra dose.
Do not make yourself vomit.
Do not stop your medicine for several days to compensate. Stopping some blood pressure medicines suddenly, such as beta blockers and clonidine, can cause a sharp rise in blood pressure or heart rate.
Do not drink alcohol that day.

How long do the effects last?

It depends on how long the medicine stays in the body. Short-acting tablets wear off within several hours. Once-daily and slow-release tablets are designed to last 24 hours or more, and amlodipine remains in the body for days. If you were advised to stay at home, expect to feel normal by the next day in most cases. Call back if symptoms get worse or new ones appear.

When the doctor doubles your dose on purpose

A different situation is a planned increase, when your prescriber raises your dose because your blood pressure is still too high. Side effects after a planned increase are usually mild and often settle within one to two weeks.

Type	Side effects that may appear or increase at a higher dose
ACE inhibitors	Dizziness, tiredness. A dry cough can occur at any dose.
ARBs	Dizziness, tiredness
Calcium channel blockers	Swollen ankles, flushing, headache, constipation with verapamil
Beta blockers	Tiredness, slow pulse, cold hands and feet
Diuretics	Passing urine more often, dizziness, cramps

Tell your prescriber about side effects that bother you or do not settle. There is almost always another medicine or dose to try. Never raise your own dose because a home reading is high. A single high reading is common and is not a reason to take more.

How to stop it happening again

Use a weekly pill organiser. An empty compartment tells you the dose has been taken.
Tie the tablet to a daily habit, such as brushing your teeth or breakfast.
Set a phone alarm, and mark the dose as taken in a reminder app or on a paper chart.
Ask the pharmacy about blister packs sorted by day and time if you take several medicines.
Keep one person in charge where a carer helps, so that two people do not each give the dose.
Keep medicines in their original boxes and store them out of the sight and reach of children.
Agree a plan in advance. Ask your doctor or pharmacist what to do if you miss a dose or take two, and write the answer on your medicine list.

What about a missed dose?

The usual advice is to take a missed dose when you remember, unless it is nearly time for the next one. In that case skip the missed dose and carry on as normal. Do not take two doses together to catch up. Check the leaflet for your own medicine, because advice varies.

To understand how doctors judge whether a medicine is working, read how to know if a medication is effective.

Common questions

Is a double dose of blood pressure medicine dangerous?

For most adults, one extra dose of most blood pressure medicines is not dangerous, but it can be for some drugs and some people. Verapamil, diltiazem, beta blockers and clonidine deserve more caution. Call for advice every time.

I took two tablets and feel fine. Do I still need to call?

Yes, it is sensible. Slow-release tablets can cause delayed effects, and the adviser can tell you what to do about your next dose.

Should I drink a lot of water or eat salt?

Drink normally. Do not load up on salt or fluids unless a health professional tells you to, especially if you have heart or kidney problems.

Can I take a second tablet if my blood pressure is high?

No. Do not adjust your own dose. If your readings stay high over several days, contact your prescriber. Seek urgent care for very high readings with chest pain, breathlessness, severe headache, weakness or trouble speaking.

My child swallowed one of my tablets. What should I do?

Call a poison centre or emergency services immediately, even if the child seems well. Do not wait for symptoms.

This guide is general education and is not medical, legal or career advice. Entry rules, fees, training lengths and treatment guidance change, so confirm them with the official body in your country or with your own doctor or pharmacist. Read our disclaimer. Found an error? Tell us.