A person can bleed to death from a limb in a few minutes. Everything below is ordered by how quickly it works.
Before you touch anybody. Your own safety, then gloves if you have them — a barrier protects both of you. Call the emergency number, or have somebody else call while you work; 112 across the European Union and the EEA, the local emergency number elsewhere.
1. Direct pressure. Press hard on the wound with whatever you have — your hands, a dressing, clothing. Hard, and without stopping. Do not lift it to look. Every check restarts the bleeding you had just stopped. If blood soaks through, add material on top and keep pressing; do not remove what is underneath.
2. Pack the wound. For a deep wound in a place a tourniquet cannot go — a groin, an armpit, a neck — push dressing or clean cloth firmly into the wound itself, filling it, and then press down hard on top of that.
3. A tourniquet, for a limb, when pressure is not enough. High and tight above the wound, over a single bone where possible, tightened until the bleeding stops. It will hurt, and that is expected. Write the time it went on, on the tourniquet or on the casualty. Do not loosen it and do not cover it: the hospital has to see it.
- A tourniquet is for a limb only. Never on the neck or the torso.
- An improvised tourniquet is worse than a manufactured one and better than bleeding out; it needs a rigid windlass to tighten it.
Then. Keep them lying down and keep them warm — a person who has lost blood loses heat and the cold makes the bleeding worse. Nothing to eat or drink. Stay with them and keep talking to them.
Do not apply a tourniquet "just in case" to a wound that direct pressure has already controlled, and do not spend time washing a wound that is bleeding heavily. Stopping the bleeding comes first.
Source. European Resuscitation Council, Guidelines 2021, First Aid section, https://cprguidelines.eu/guidelines-2021 ; the Stop the Bleed programme of the American College of Surgeons, https://www.stopthebleed.org/ ; World Health Organization, Prehospital trauma care systems, https://www.who.int/publications/i/item/prehospital-trauma-care-systems
What this is not. Reading, not certification. Nothing here replaces accredited first-aid training and it must not be relied on in place of it.