This image shows an Insulin pump being worn on a patient's left hip.
The black box contains an insulin cartridge and pump and delivers a constant trickle of fast-acting insulin via the tubing to a sub-cutaneous needle. The patient wears the pump 24 hours a day. Boluses of fast-acting insulin can be delivered via the pump when the patient is eating meals or snacks.
This system can bring excellent control but is not suitable for everyone.
If there is an interruption to the delivery of insulin by the pump (eg cannula blockage or pump removal) the patient is at high-risk of developing DKA within hours due to the absence of active insulin.
Cropped image from Alden Chadwick via Flickr, used with Creative Commons License