Constitution
The hitpoints skill: every level raises your health pool and everything that heals or damages you runs through it. The French translation is literally ‘Points de vie’.
Constitution is your health bar and nothing else. You start with 100 health at level 1 and every level adds a flat 10, so 1,080 at 99 and 1,290 at 120. Each level also adds a quarter of a point to your combat level, it decides how far a piece of food goes, and at 70 it opens the barrier into the Zamorak stronghold in the God Wars Dungeon. You never train it on purpose.
Level 1 to 120
It comes off the damage you deal, always. Ranged and magic pay roughly a point for every 12 damage; melee pays a point for every 22 or so, which means an archer banks it at close to double a warrior's rate. So the shape of the grind is just the shape of your combat: small animals, then giants and slayer tasks, then dragons, then bosses with five figure health bars. Nothing else moves it.
- Cows, chickens and goblins around Lumbridge 1 to 20
Anything with a health bar counts. Cows are 85 health, goblins 70, chickens 60, and with a bar of only a hundred or so yourself the early levels arrive fast.
- Rock crabs and hill giants 20 to 40
230 and 300 health apiece and they hit softly, so you can chain them without burning food. Hill giants stand in the Edgeville dungeon among other places, which is also where Vannaka hands out slayer tasks.
- Moss giants and your first slayer tasks 40 to 60
Moss giants are 700 health, ankou 450, demons 600. Slayer tasks start paying properly around here and they pay constitution at the same time, so take them and get both.
- Slayer Tower and Pollnivneach monsters 60 to 80
Dust devils, greater demons, gargoyles and abyssal demons all sit between 750 and 850 health. An abyssal demon is worth roughly 70 constitution XP killed with ranged or magic and only about 38 with melee.
- Dragons 80 to 99
Green, blue, red and black dragons carry 1,400 to 2,200 health each. Long fights, so a lot of damage banked per kill, and they drop well enough to be worth the trip on their own.
- Bosses 99 to 120
The last stretch is all five figure health bars: the kraken at 6,500, Dagannoth Rex at 8,000, the Kalphite Queen at 10,000, the King Black Dragon at 15,000, and the God Wars generals and the giant mole at 20,000 each.
Regeneration is flat and slow
You heal a fifth of a health point a second, twelve a minute, and that rate never changes with your level. At 99 that is an hour and a half to refill an empty bar. The Constitution cape is the only item that touches it, and it doubles the rate.
Healing prayers dwarf all of that. Rapid heal at 20 Prayer adds 5 health a second, fast heal at 50 adds 8 and super fast heal at 80 adds 12, and those stack straight onto the base tick. On a long trip a heal prayer is worth more than a backpack of food.
Food
What a piece of food heals is fixed, so it is worth less and less as your bar grows: cooked shrimp 20, cooked trout 90, cooked lobster 140, cooked swordfish 150, cooked shark 225, cooked manta ray 255, cooked dark crab 270, cooked eel 285. Cooking matters: raw shrimp heals 10 against 20, raw shark 150 against 225.
Food only works when you are below full health. The exception is the cooked meals that carry a buff, the pizzas, the salads, the apple pie and the tuna potato, which you can eat topped up just for the effect. Do not click while facing a fire, or nothing is eaten at all.
What the level unlocks
At 70 you can pass the darkness barrier into the Zamorak stronghold in the God Wars Dungeon. It costs 100 prayer points every time, unless you have submitted to Saradomin's light inside, after which the darkness leaves you alone.
Because constitution feeds your combat level at the same weight as defence, it quietly decides which ordinary monsters slayer masters will offer you and which boss tier Sumona draws from.
Worth knowing
- Ranged and magic pay about a point of constitution for every 12 damage dealt; melee needs about 22 for the same point.
- Witch's House pays 6,325 constitution XP, the Fremennik Trials 2,812 and Nature Spirit 2,000.
- Your health carries between sessions. Log out hurt and you log back in hurt.
- The Constitution cape doubles your passive regeneration and cuts prayer point use by 5%. The 120 version carries the same perks.
The full table
Level 1 to 9 2 entries
Level 50 to 59 2 entries
Book of balance Offhand god book. At 50 Constitution it grants +25% max prayer points, a 5% prayer-point reduction and a +3% melee, ranged and magic damage buffer. Repairing the damaged book from the four Guthix pages at a prayer altar is itself a 50 Prayer check rather than Constitution, though the in-game wiki files this entry under Constitution 50. 50 
Unholy book Offhand god book, occupies the shield slot. Item extra skill=constitution, level=50: +25% max prayer points and a +6% melee/ranged/magic damage buffer once Constitution is 50. Repaired from the 4 Zamorak pages at a prayer altar (that repair step needs 50 Prayer). 50 Level 70 to 79 2 entries
Level 90 to 99 3 entries
99 Constitution cape Buyable for 100,000 coins from the skill-cape shop once Constitution is 99, and it will not equip below that. It doubles passive health regeneration, on top of a 5% prayer-point reduction and a +20 defence buffer. 99