Transfusion

At 1st level, You can spend one spell slot of first level or higher to target a creature within 20 feet of you. The creature must make a Constitution saving throw. On a failed save, the target takes 3d6 piercing damage, or half as much on a successful save, and you heal for half the damage (rounded down) as their blood is pulled from their body and absorbed into yours. 

At higher levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.