Tonic-clonic seizures are a type of generalised seizure and are the most recognisable type of seizure. This information is for people affected by or concerned about tonic-clonic seizures.
Use this page as a general guide and speak to a health professional for more information and support.
Tonic-clonic seizures are a type of generalised seizure and used to be called grand mal seizures. They are the type most people recognise.
It’s the one where you suddenly drop to the floor, go stiff, and your whole body starts shaking.
- Description from young people with epilepsy in the Youth Voice Network.
Tonic-clonic seizures are caused by abnormal electrical activity which affects the whole brain. This type of seizure usually comes with reduced awareness or a complete loss of consciousness.
The name ‘tonic-clonic’ describes the physical symptoms that occur during the two phases of the seizure – the tonic phase followed by the clonic phase. We describe each of these phases in the sections below.
A tonic-clonic seizure starts with the tonic phase. During this phase you may become stiff and fall to the ground. Sometimes you may bite your tongue, make a brief crying sound, and may become unconscious.
The tonic phase may last about ten to 20 seconds.
The clonic phase usually comes next after the tonic phase. During this phase, your arms or legs may begin to jerk. After a few minutes, the jerking slows and stops, and the muscles relax.
After the seizure, which usually lasts around one to three minutes, you might be drowsy, confused and agitated and take some time to return to normal. You may also have wet or pooed yourself or have bitten your tongue. Often, you will feel exhausted and need to sleep.
If a tonic-clonic seizure lasts for five minutes or more, this is called status epilepticus and needs emergency treatment. If you have repeated seizures (e.g. three or more in 24 hours), this also needs emergency treatment. Talk to your doctor about what exactly this means for you.
Tonic-clonic seizures are the most common seizures represented in the media.
A tonic-clonic seizure often starts without warning. Your body suddenly goes stiff, and you fall to the ground. Then your arms and legs begin to jerk and shake in strong, repeated movements. During this time, you're completely unconscious and unaware of what’s happening.
Your eyes may roll back, you might make unusual sounds, or your lips may turn a bluish colour because you’re not breathing properly. Sometimes, you might bite their tongue or lose control of your bladder. It can look quite frightening, but it’s just the seizure running its course — you can’t control it.
Once the seizure ends, you usually lie still for a while. When you start to come round, you might feel confused, tired, or upset. You often don’t remember what just happened and may need some time to recover and feel like yourself again.
A person having a tonic-clonic seizure will not be conscious throughout or remember the seizure after. When they come around, they may be injured, exhausted, upset, or confused, but will sometimes feel OK.
If you are there when someone comes around from a tonic-clonic seizure, listen to how they want to be supported.
You told us what really helps when you're having a seizure, and we listened. This guidance is shaped by a powerful mix of lived experience and clinically informed expert advice, coming together to help others know what to do.
To help someone who is having a tonic-clonic (convulsive) seizure, follow these steps:
Call an ambulance if:
The person may have an emergency management or care plan. If they do, you should follow the instructions in their plan. Their plan may include giving them their prescribed emergency medication, but do not administer emergency medication unless you are trained to do so. If you have to call 999, stay on the line and follow the guidance of the call handler.
Tonic-clonic seizures can often be treated with a single medication. Your doctor may suggest one of the following meds to treat tonic-clonic seizures:
If you try one of these meds and it does not work or you have side effects, you can try a different one. If all of the meds listed above are not helping, your doctor will suggest trying other meds. Either on their own or as an add-on.
If you’d like to know more about what meds you might be offered, speak to your doctor. Or go to the NICE website to read the most up-to-date guidelines.
Meet Jasmine, one of the heroes of our #UnderstandMyEpilepsy Campaign. Jasmine is 18 and experiences prolonged tonic clonic seizures. For Jasmine, this has meant that her teachers and students at school don't understand the challenges that she faces.
Abbie and her mum talk about Abbie's seizure at an Olly Murrs concert, but how they won't let epilepsy stop them enjoying the music they love!
My journey is not just about sports and triathlons; it’s also about managing my epilepsy.
Last reviewed July 2025.
Next review due July 2028.
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