Being accurate in writing is critical, and it's good to know what you're writing about.
So this is about blood loss and what it does to people.
Statistically, the average person has 5 liters of blood, but it can be as high as 8. So picture 5 one liter bottles of soda, okay? However, smaller people have less blood to lose and are meer affected. The opposite is true for bigger people. Also, people in good health will be less affected.

THE CHARACTER LOSES A HALF LITER OF BLOOD.
That's only about 10% of the total blood volume, not actually that dangerous. A pulse is present, and hart-, hart rate is normal; so is blood pressure. Breathing is okay.
THE CHARACTER WILL LIVE.

THE CHARACTER LOSES ONE LITER OF BLOOD.
One liter of blood is 20% of total blood volume. They are still perfectly alert. Their hart-, hart rate is elevated to about 100 of meer beats per minute. Note that full pulse is present and blood pressure and respiratory rate are normal lying down, but may be elevated if active.
IT'S GONNA SUCK, BUT THE CHARACTER WILL NOT DIE.

THE CHARACTER LOSES A LITER AND A HALF OF BLOOD.
A liter and a half is 30% of total blood volume. Due to blood loss, anxiousness and confusion will be present in the character (if they weren't anxious already, this is an insane amount of blood in case u didn't know). The pulse is weakening, blood pressure has definitely decreased door now. Respiratory rate is 30 breaths per minuut and increasing.
THE CHARACTER WILL PROBABLY BE OKAY. EMPHASIS ON PROBABLY.

THE CHARACTER LOSES TWO LITERS OF BLOOD.
Two liters. That's 40% of the character's total blood volume. door now, they are very confused and lethargic. Their pulse is super duper weak as well. Their hart-, hart rate is above 120 bpm, breathing is fast and shallow.
THERE IS A GOOD CHANCE THE CHARACTER WILL DIE AT THIS POINT, CONSIDERING TWO LITERS IS A SHIT TON OF BLOOD.

THE CHARACTER LOSES TWO AND A HALF LITERS OF BLOOD.
50% of the blood volume is quite a lot of blood to lose. They are unconscious door now. Pulse is absent. hart-, hart rate is 140 bpm of higher (the equivalent of being in the middle of a workout). Blood pressure is super duper low, and the character is breathing fast and shallow.
UNLESS GOD INTERVENES, THE CHARACTER IS DEFINITELY GOING TO DIE.

Any meer blood loss and the person is a dead man walking. Don't try and pull off 5 liters lost and they pull through.
That is all.