Tonic-Clonic Seizures Explained: What Happens and How to Respond

A tonic-clonic seizure is the type most people picture: the body stiffens, then jerks rhythmically, and the person is unconscious throughout. Most last between one and three minutes. The response is to time it, protect the person from injury, avoid restraining them, place them in the recovery position once the movements stop, and call 999 if it passes five minutes or meets the other emergency criteria.

What is a tonic-clonic seizure?

A tonic-clonic seizure is a seizure with two distinct phases: a tonic phase in which the muscles stiffen, followed by a clonic phase of rhythmic jerking. The person is unconscious throughout and will have no memory of it.

The term “grand mal” is outdated. Epilepsy Action notes it is sometimes still described as a convulsive seizure, but tonic-clonic is the current term.

There are two routes to one:

• Generalised onset tonic-clonic. The seizure involves both sides of the brain from the start, with no warning.
• Focal to bilateral tonic-clonic. The seizure begins in one area and spreads. The person may have a warning, previously called an aura.

Our overview of the different seizure types sets out where tonic-clonic seizures sit alongside focal and absence seizures.

What happens during one

Knowing the sequence helps staff stay calm and respond appropriately.

Tonic phase. The muscles stiffen. If the person is standing they will fall, often without protecting themselves. Air forced past the vocal cords can produce a cry or groan, which is not a sign of pain. Breathing may appear to stop briefly and the lips may look blue or grey. This phase is usually short.

Clonic phase. Rhythmic jerking of the limbs begins and gradually slows. The person may bite the inside of their mouth or tongue, and bladder or bowel control may be lost.

After the movements stop. Breathing returns to normal, often noisily. The person remains unconscious at first, then gradually regains awareness.

Most tonic-clonic seizures last between one and three minutes.

Seizure first aid, step by step

The steps below reflect current guidance from Epilepsy Action, the Epilepsy Society and the NHS.

1. Note the time immediately. Everything else depends on knowing how long the seizure has lasted.
2. Clear the area. Move furniture and hazards away rather than moving the person, unless they are somewhere genuinely dangerous such as a road or water.
3. Protect the head. Put something soft underneath it, or cup it in your hands. Remove glasses.
4. Loosen anything tight around the neck, such as a collar or tie.
5. Stop people crowding round. Privacy and dignity matter, and a smaller audience makes recovery easier.
6. Look for identification. A medical ID bracelet or epilepsy card may set out the person’s own emergency protocol.
7. Do not hold them down. Restraint causes injury and does not shorten the seizure.
8. Do not put anything in their mouth. It is not possible to swallow the tongue, and objects cause serious harm.
9. Once the jerking stops, place them in the recovery position. On their side, with the head tilted and the mouth pointing down so the airway stays clear.
10. Stay until they have fully recovered. Do not offer food or drink until you are certain they are fully alert.

When to call 999

Most seizures in a person with diagnosed epilepsy do not need an ambulance. Call 999 if:

• It is the person’s first known seizure
• The convulsive seizure lasts more than five minutes, or two minutes longer than is usual for that person, or you do not know how long their seizures usually last
• One seizure follows another without recovery in between
• They have had three or more seizures in the past 24 hours
• They are seriously injured
• They have difficulty breathing after the seizure has stopped
• The seizure happened in water, or they may have inhaled or swallowed water
• They do not recover as they normally would

NICE guideline NG217 defines convulsive status epilepticus as seizures lasting five minutes or more, and it requires immediate emergency treatment. Our articles on status epilepticus and communicating with emergency services go further.

Where a person has a prescribed emergency medication protocol, follow it exactly as written. Staff must be signed off as competent before administering anything.

The recovery period

The seizure ending is not the end of the event. Recovery, known as the post-ictal phase, can last from minutes to many hours.

Expect confusion, deep tiredness, headache, muscle soreness and low mood. Some people are briefly agitated or want to move about. Speak calmly, explain what has happened, and repeat it as needed.

Practical priorities are dignity, privacy and a quiet place to rest. If incontinence has occurred, handle it discreetly. Our guide to post-ictal care covers the hour afterwards in detail, and every seizure should be recorded in full.

Why seizure control matters

Tonic-clonic seizures carry the highest known risk of sudden unexpected death in epilepsy. Epilepsy Action identifies uncontrolled tonic-clonic seizures as the biggest risk factor for SUDEP, with risk rising as seizure frequency rises. Deaths often occur during sleep, which suggests seizures during sleep may carry additional risk.

Accurate recording is therefore not administration. It is the evidence a clinical team uses to decide whether treatment needs reviewing.

Frequently asked questions

How long is too long?
Five minutes. At that point a convulsive seizure meets the definition of status epilepticus and needs emergency treatment.

Should I put them in the recovery position during the seizure?
No. Wait until the convulsive movements have stopped, then turn them onto their side.

What if they stop breathing?
Brief interruption during the tonic phase is expected. If normal breathing has not returned once the movements stop, call 999 and follow the call handler’s instructions.

Do they need to go to hospital every time?
No. For someone with diagnosed epilepsy and an established pattern, hospital is needed only when the criteria above are met.

Can a seizure be stopped?
No. It must run its course. The role of the person nearby is to keep them safe and time it.

Make sure your team knows exactly what to do in the first five minutes

Seizure first aid is simple, and it is the detail that gets missed under pressure: timing it, leaving the person alone, knowing the 999 threshold. National Epilepsy Training delivers epilepsy awareness training, with buccal midazolam competency where your setting needs it.

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