Thieves broke into a storage area at Queen Alexandra Hospital in Cosham at around 2.40am on Friday morning.
A large van with three men inside, drove into the medical facility and stopped near to the storage area of Nitrous Oxide canisters
Two men got out of the van and forced their way into the storage area and then they put nine canisters inside the van and drove off.
Portsmouth Hospitals NHS Trust, which operates QA, have said that the burglary will not ‘affect the day to day running' of the hospital.
Luke Groves, interim director, medicines optimisation and pharmacy at the trust, explained: ‘Nine canisters of nitrous oxide were stolen from a locked storage unit outside the hospital in the early hours of Friday.
‘While this theft has not affected the day to day running of the hospital we are incredibly disappointed that anyone would steal from their local hospital.
‘We have reviewed and are increasing on-site security, including around our outdoor storage.
‘We would like to emphasise the dangers relating to the misuse of nitrous oxide.
‘Side effects can include nausea, vomiting, dizziness, disorientation and headaches.
‘The misuse of this anaesthetic substance can also cause breathing difficulties, seizures and even death.’
Nitrous Oxide, which is commonly known as laughing gas, has a number of legitimate uses.
However, in the wrong hands it has also been used as a recreational drug.
Police are keen to speak to anyone who has been offered any of these items of sale, or anyone who knows who may be responsible for this incident.
Anyone who has any information about this incident or anyone offered these canisters for sale should call 101 quoting the crime reference number 44190020822.