The pharmaceutical company behind injectable weight-loss drugs has been accused of prioritising profits over the health of people in developing countries by halting production of its insulin pens.

People living with type 1 diabetes who are reliant on the human insulin produced by Novo Nordisk, will instead be given glass vials and syringes – which they say are inconvenient and harder to use with the same accuracy.

Novo Nordisk has told governments and non-profit organisations that it will no longer be producing human insulin in pens and has already stopped supplying in South Africa, where patients have had to switch to glass vials.

Campaigners claim the move is to allow the scaling-up of the production of injectable weight-loss drugs such as Ozempic and Wegovy.

Novo Nordisk this year announced a $4bn (£3bn) investment in a production plant in the US to “grow its ability to produce current and future injectable treatments for people with obesity and other serious chronic diseases”.

Lecritia Roberts, 31, from South Africa, has type 1 diabetes. She said it feels as if the clock has been turned back on treatment.

“It makes me angry. They don’t understand how much harder they are making our lives,” she said. “Why are they making things more convenient for people who want to lose weight over people struggling with a disease?”

Roberts used vials to inject insulin as a teenager but said it was difficult to accurately administer, was often embarrassing in public and required a lot of caution, as dropping the bottles could result in losing a month’s worth of medicine in one go.

She said the pens transformed how she managed her diabetes because they were easier to carry and could be discreetly used, even while at her desk at work.

“When I was younger it was challenging, I didn’t like injecting. Sometimes I injected it into the floor because I didn’t like having the needle in my arms or thighs,” said Roberts. “If your break the vial and don’t have any [saved] back, you basically don’t have any insulin unless you buy it, but people in rural areas can’t afford it.”

She said she had recently seen a blind diabetes patient in hospital having to learn how to use the vials and feared for her – the clicking sound made by a pen helps people with visual impairments to measure dosage.

A survey by the medical charity Médecins Sans Frontières (MSF) and T1International, which campaigns for people with type 1 diabetes, found that 82% of patients preferred pens over syringes and vials.

Novo Nordisk will continue to produce pens for analogue insulin – synthetic substances that are more costly than human insulin, putting them out of budget for many in developing countries.

Candice Sehoma, advocacy adviser for MSF’s Access Campaign said Novo Nordisk’s decision would result in unequal care around the globe, and pointed out that syringes and vials are outdated and rarely used in wealthy countries.

“While the corporation continues to profit immensely by supplying newer, more expensive insulin and semaglutide pens (Ozempic and Wegovy) to wealthier nations, its decision to withdraw human insulin pens may push people with diabetes in resource-limited settings, who rely on insulin for survival, to revert to using vials and syringes, which virtually nobody uses any more in high-income countries,” she said.

Novo Nordisk denied that the discontinuation of insulin pens was to make way for the production of weight-loss drug pens, saying that a different type of device was used. A spokesperson said it was phasing out products to address “capacity constraints”.

“Patients in a number of countries, including South Africa, will eventually have limited access to our human insulin in pens,” the spokesperson said.

“We recognise the impact these decisions will have on patients and we are in dialogue with local health authorities to ensure that patients continue to have access to the treatment they need. We will continue to deliver our newer insulins in pens.”

The scientists who discovered insulin assigned the patent to the University of Toronto to ensure its accessibility, but today more than 90% of the medication’s production is in the control of three companies. The same firms produce the new weight-loss drugs, developed initially to treat diabetes, and have been accused of having a “stranglehold” on that market, charging up to 400 times more than needed for products.

MSF has called on other insulin manufacturers to guarantee lower prices for all types of the devices, which it says could still be profitable at $1 a pen.

“The profiteering on a lifesaving medicine that has been available for more than a century must stop now,” said Sehoma.