Yes. When taking damage, red hearts can be healed through a random enemy drop or frequent chest drops. As such, you can regain your health multiple times throughout your run. Blue hearts, on the other hand, cannot be healed. Blue hearts cannot be regenerated throughout your run, but, on occasion, you may be able to gain one or a fragment of one through a tarot card or the odd chest drop. When using vampiric weapons, there is a small chance you'll gain a blue heart fragment, but it's far from guaranteed.