Whangārei Hospital has had a longstanding problem with people stealing food belonging to patients and caregivers, a senior manager says.

Jeanette Wedding, general manager of several Northland District Health Board departments, including district hospitals, said theft of food from communal fridges was a problem but was not one unique to Northland hospitals.

She was responding to recent reports about food and drink being stolen from the Whangārei Hospital children's ward kitchen and also the alleged find of a small bag of methamphetamine on the ward's floor.

Northland DHB received a formal written complaint on Tuesday from a patient's family member about concerns regarding what they thought was a "P" bag found in the children's ward, along with theft of food from a communal kitchen, Wedding said.

"We will enter into a formal process to investigate the complaint and will respond to the complainant over the next few weeks regarding this matter.''

The board took all complaints seriously and strongly encouraged people to speak to managers at the time of concern so it could be investigated at the earliest possible opportunity, she said.

"Northland DHB encourages parents and caregivers to stay with their children and subsequently our children's ward is an extremely busy, family centred environment.

"It is very disappointing that food goes missing, especially when parents and caregivers are there to care for and focus on their children, not worry about whether their food will be taken.''

A woman staying in Whangārei Hospital with her sick baby said she found a bag of methamphetamine on the floor of the children's ward corridor. She handed the Class A drug in to security services and laid a formal complaint with the hospital's management, her partner said.

Allan Trow said the incident happened at the weekend and had upset him and his partner.

"Kids run up and down those wards. What if one of them picked up that bag up and swallowed its contents? It could kill them.

"What kind of people take P into a children's ward in a hospital?"