This is what I did when I had to. Next time I will make sure I have 20 or more needles for a cycle (when only once weekly shots.) Held the needle (not plastic syringe -- it maight melt) in boiled water for 20 seconds or more. Took some water into syringe and expunged back right away (again you don't want the plastic syringe to melt at all.) Then held the needle 20 seconds in rubbing alcohol to further disinfect. That's what I did. And, yes, it does get dull. If I had several old needles, I would use whichever have been reused the least. I injected into thigh because of no body fat under the skin. So I didn't have to push through fat with a dull(er) needle. This is what I did with no problems. I don't know anything about using bleach so cannot say. I'm not telling you what to do, but only what I had to do when in the same position. I rubbed alcohol on the inj site prior. I even put needle into hydrogen peroxide after the alcohol. I did not want to take any chances. Hydrogen peroxide is an anti-infective for when you get a cut, so it made sense to use also.