Mayor Bloomberg yesterday defended a Health Department pamphlet that teaches heroin addicts how to shoot up safely — because, he said, while no one should use hard drugs, the city has an obligation to diminish the risks for those who do.

“It’s certainly not in the interest of society to have you get HIV/AIDS,” he said.

The pamphlet is being blasted as a heroin “how-to,” as the 16-page booklet features seven comics-like illustrations and offers dope fiends such useful advice as “Warm your body (jump up and down) to show your veins,” and “Find the vein before you try to inject.”

It even encourages addicts to keep jabbing if their needles miss the mark.

“If you don’t ‘register,’ pull out and try again,” it says.

READ: HEROIN FOR DUMMIES: CITY FLIER ‘SMACKS’ OF LUNACY