Health Heavy Dr. Mundo is nearly impossible to kill. His abilities do percent health damage and his passive regenerates percent health. All of his attacks cost health so getting a lot early will make you more able to get early kills and dominate the lane. Start with Flat Health Runes for early game sustain and build health items. Learn to make your skill shots count and bush check regularly with your Infected Bonesaw. Dr. Mundo is a harassment champion early game. Get a point in your Q and use it to last hit safely while you poke at your opponent.

Get Warmog's Armor as soon as you can. The health boost and regeneration will make for inhuman sustain. Add armor or magic resist later as needed. Magic Pen items like Sorcerer's Shoes are a good way to boost damage from cleavers and burning agony without giving up a valuable slot to attack items you won't use late game anyway. Mundo has no burst damage abilities. His Q and W attacks do magic damage but do not improve with AP items. All Dr. Mundo abilities are tied to health. Spirit Visage is a good item to work on next as it will boost healing even further.

Have your Sorcerer's Shoes and no place to go? Adding Randuin's Omen can be useful against burst damage hits and Sunfire Aegis or Liandry's Torment makes a nice compliment to your Heart Zapper AOE and Infected Bonesaw damage. If you are building to support, try Locket of the Iron Solari to boost allies health regen and magic def as well as adding a shield ability for team fights.