Recall of some insulin pens ordered
The medicines watchdog, the MHRA, is urging people with diabetes to check their insulin pens.
It says a manufacturing fault has led to some batches of pens or cartridges containing the wrong amount of insulin.
The products affected are the NovoMix 30 Flexpen 100U/ml pre-filled pen and the NovoMix 30 Penfill 100U/ml cartridge.
Last year there were just over a million prescriptions for these products dispensed in England.
They are used mainly by children with type 1 diabetes, though some people with type 2 diabetes also use the pens.
The MHRA warning has also been circulated by the Department of Health in Northern Ireland.
Insulin is used to regulate blood-glucose levels.
The Medicines and Healthcare products Regulatory Agency says patients with pens affected by the recall should consult their GP or nurse to arrange for a new supply as soon as possible.
In the meantime patients should not stop their treatment, it said.
The Agency has issued a list of batch numbers printed on the pen or cartridge. It says only a small fraction of the cartridges sold are likely to have been affected.
The batch numbers are: CS6D422, CS6C628, CS6C411, CP50912, CP50750, CP50639, CP51706, CP50940, CP50928, CP50903, CP50914, CP50640, CP51095, CP50904, CP50650, CP51098, CP50915, CP50412, CFG0003, CFG0002, CFG0001, CP50902, CP50749, CP50393, CP50950, CP51025, CP50751, CP50375, CP50420, CP51097, CP50641, CP51096 and CP50392.