Inaccurate weighing scales are a danger as they could lead to patients being given the wrong doses of drugs, the Department of Health has warned.
It has told that in GP surgeries, nursing homes and hospitals some scales were incorrectly calibrated or were also the wrong type.
In February, it emerged NHS staff had used defective bathroom scales to weigh a four-year-old cancer patient in order to calculate her radiation dosage. It was reported at the time that the error was spotted before any damage was done.
The alert published from the Department of Health said scales relating to medication, treatment or diagnosis and should be of the Class III type and must all be checked by mid June.
Any domestic scales that are being used must be removed and replaced with medical scales in most places.
The government insisted that the alert related to both adults and children.
But Tam Fry, from the Child Growth Foundation, said he had proof that many children are not weighed on Class III scales and that the alert should have discussed the needs of children specifically.
A Department of Health spokesman said: "Weighing scales of the Class IV category should only be used in healthcare premises in GP consulting rooms or by community health visiting staff for monitoring.