You only get dodge prediction when you use the GETINDARE glyph or the quicksilver potion. After you dodge once, you lose dodge prediction and don't know until you actually attack the enemy whether you're going to dodge or not.
These are the following ways you can heal when you attack:
1) you level up
2) you have lifesteal
3) you're standing on a blood pool while at full health with sanguine, you attack the enemy (taking damage), and then attack him again, you will drink the blood pool and heal
(that last one is kinda convoluted, but it can happen)