From Brotato Wiki
Item
Medical Turret is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.
Buying the item spawns a Turret at the beginning of each wave that shoots healing projectiles towards you while you are within 400 range for 3 + (5% ) healing every 2.2 seconds.
Note that the engineering scaling rounds down. So it takes 20 or more engineering for the turret to heal 4 HP. While it only takes -1 or more engineering for it to only heal 2 HP per shot.
Scaling
Turrets are unaffected by Primary Stats, such as % Damage, Life Steal, Attack Speed, Crit Chance. But is affected by Engineering & Range.
Turrets are affected by Secondary Stats such as piercing and bouncing granted by the items Bandana & Ricochet. Not that turrets deal 100% even on bandana pierces, and ignores the -50% damage per pierce. Explosive Turret benefits from Explosion Damage and Size granted by Dynamite & Plastic Explosive. Turrets can inflict burning with Scared Sausage, and Snake helps Incendiary Turret inflict burn to more targets.