Associated risks
Nasty and potentially fatal health complications can be caused by intravenously using drugs. These include: 

• Blood-Borne Viruses, such as Hepatitis B and C and HIV.
• These can be contracted by sharing needles and paraphernalia. In some cases Hepatitis C will develop into chronic conditions such as cirrhosis of the liver or liver cancer. There is no vaccine for either Hepatitis C or HIV.
• Abscesses - ugly 'holes' and lumps in the skin often caused by 'missing' the vein.
• Viral and bacterial infections.
• Overdose.
• Vein damage - collapsed and severely weakened veins from over use of one part of the body.
• Cellulitis - serious skin infection.
• Septicemia - Blood poisoning, can be fatal if untreated.
• External ulcers.
• Deep Vein Thrombosis or blood clotting - blocked veins can be extremely painful if untreated and can be fatal. Clots can remove themselves and cause heart failure or lung damage.
• Endocartitis - inflammation of the heart lining - can cause heart failure or infections to grow in the heart wall.
• 'Hitting' An Artery - may result in severe blood loss, and/or loss of limbs, especially if injecting into sites near an artery such as the wrist or groin.