Can I reuse a needle?

No. Sterile, single-use equipment is the standard, and reuse is not a corner worth cutting.

Why, specifically

• Sterility cannot be restored. Once a needle has been unsheathed and used, it is contaminated. Wiping with alcohol does not resterilise it, and there is no home process that does.
• Needles dull immediately. A hypodermic point is ground to a fine edge that deforms on first pass. A reused needle tears rather than cuts, causing more tissue trauma and more pain.
• Coring. A dulled point can punch a fragment out of a vial stopper and carry it into the solution.
• Vial contamination. Reusing a needle between the vial and anywhere else risks introducing organisms into a multi-dose vial, which then affects every subsequent draw. This is the reason bacteriostatic water contains a preservative at all — and a preservative slows growth, it does not sterilise.

Disposal

Used sharps belong in a rigid, puncture-resistant sharps container, not household waste. Many pharmacies and local authorities operate collection schemes.

This is standard sterile technique rather than a judgement call. Research use only. Not medical advice.