how long does it take to die after slitting both your wrists vertically?

Let me add and make things more clear, for educational purposes, of course. There are two thin bones that make up the forearm, right, feel them. Between them there is an artery. The difference between an artery and vein is that an A*rtery takes blood A*way from the heart, allowing a quick beed-out (exsanguination). Vein takes oxygen-poor blood back to the heart. It's in the word vein and venial to mean shallow. The sheer diameter of the tube means there is a very clear difference between arterial and venial exsanguination. You would need to have massive crushing injuries to effectively, not bleed-in. At that point it would take hours to fail to get oxygen to your brain. A tiny arterial rupture of any sort, even a kick to the groin, can cause death in minutes because losing all your oxygen supply at once shuts off the heart and brain.

If you leave with one fact to answer your question, think about how the morning news calls i-203, the 8 lane interstate an a*rterial route where the old highway next to it can't pass a bike and a car at once.

With enough blood loss, a person can die in under a minute. On average, you only need to lose a couple liters of blood to die, but in some rare instances, people have survived losing half of their blood, even half of their body.

You die from blood loss because your heart is starved of oxygen and blood pressure, everything immediately shuts down because the organs aren't being fed. It only takes 20 minutes after that for you to suffer total, irreversible brain damage and be considered completely dead. It's possible to revive someone who's heart has stopped from blood loss if given immediate and intensive care, but unlikely.

I haven't seen 13 Reasons yet, but it sounds like she opened up the veins in her arms and she died of blood loss. Being in bath water negligibly allows the blood the flow faster, but not much. It all really depends on how deep the wound is. You can open the vein vertically or horizontally, but blood will flow out regardless, if it's deep enough.