The vacuum should be as high as you can tolerate comfortably, not it should not hurt. Higher vacuum does not necessarily remove more milk because a pump doesn't suck milk out of the breast, it only stimulates your breast to release the milk with your own letdown reflex. But turning the suction too low will not remove milk effectively. It's about finding the balance between strength and comfort. You might even find that you need to change the level during a session as less milk is in the breast. Play around with the settings to see what works best for you.
Reviewed by Diana West, IBCLC
June 10, 2021