I feared my son had a brain tumour but he'd been poisoned with vitamin D

When seven-year-old Roo suddenly became unwell last year - losing weight and guzzling water - his doctors and parents feared he might have a brain tumour.

But investigations found he had been accidentally poisoned with an overdose of vitamin D that had been prescribed for growing pains.

Roo's bottle of vitamin D3 drops - which were about seven times more concentrated than they should have been - was from one of two bad batches distributed across the UK.

The dosage gave Roo an acute kidney injury and a leading expert has told BBC News the young child would have died if he had finished the prescribed course.

Vitamin D is a vital nutrient that regulates calcium and phosphate for healthy bones, teeth, and muscles. It is taken as an over-the-counter supplement by millions of adults.

However, higher dosage Vitamin D, which is prescribed by doctors, is still classed as a food supplement and not regulated by the medicines regulator, the MHRA.

Instead, vitamins and food supplements are monitored by the Food Standards Agency.

The MHRA said it worked together with the FSA to keep the public safe.

But a leading expert has told BBC News the medicines watchdog should look at changing the way vitamin supplements are regulated.

Roo was prescribed a high dose of vitamin D3 drops for 12 weeks in December 2024 to try to ease intense pain in his legs.

It came after he had been referred to paediatricians at Crosshouse hospital near his home in Kilmarnock, Ayrshire.

Blood tests showed him to be fit and healthy apart from a slightly lower than normal level of vitamin D.

He was given supplements containing vitamin D3 – also known as colecalciferol – to raise the levels in his blood.

Over the next few weeks, Roo became sleepy and lost his appetite.

He began to lose weight and started guzzling water "like he was in a desert", his mum, Carys Hobbs-Sargeant, said.

Roo also had bouts of vomiting all through January and struggled to eat.

"He was really sick," Carys said.

"He lost more than 10% of his body weight over that six weeks. He had these huge baggy eyes and he was so tired and he just couldn't eat."

When Roo saw the paediatrician again, he was admitted to hospital straight away.

Initial blood tests showed Roo had an acute kidney injury, and his kidneys were extremely dehydrated so doctors began searching for the cause.

They did not initially have concerns about the vitamin D prescription, as he was only two-thirds of the way through a course of the recommended dose.

But his condition continued to deteriorate.

"He became hypercalcaemic, and they were very concerned that his calcium was so high in his blood," his mum Carys said.

"They were looking at whether it was a brain tumour, and we were sort of gearing up for him to have an MRI of his brain."

Roo's mysterious case was also being reviewed by teams at Glasgow's Royal Hospital for Children and it was a chance phone call with one endocrinologist there that provided the missing piece of the puzzle.

A colleague in Manchester had asked him if they had seen any of a "bad batch" of vitamin D3.

With details of the batch, Roo's team were able to cross-reference with the bottle he was still taking drops from every day.

"We flipped from it was his body doing something weird to he's essentially been poisoned by this bad batch," said Carys.

"You felt relieved and lucky and angry all at the same time that it wasn't cancer, but it was something that had happened to him. It's poisoning, essentially."

Roo's bottle of drops was matched to one of two faulty batches of Aactive D3 supplements from TriOn Pharma, which were distributed across the UK.

The drops were seven times the concentration they should have been.

The faulty batches were recalled by the Food Standards Agency (FSA) on 9 January but its Scottish - Food Standards Scotland (FSS) - which was responsible for the recall north of the border, said the alert did not reach the right departments.

The investigation also found that the Ayrshire pharmacy which dispensed the drops did not pick up the manufacturer's recall email until nearly three months after it was issued.

A medicines alerts from the MHRA would have gone to the pharmacies high-priority clinical inbox - and should then have been read straight away.

Prof Stuart Ralston of the University of Edinburgh is a former chair of the MHRA's Commission on Human Medicines. He said Roo's shocking case illustrates why the MHRA should consider taking over the regulation of vitamin supplements.

"The product was estimated to have seven times the amount of vitamin D that he should have had," he said.

"I have not come across that in a career of over 40 years.

"He was meant to have a 12-week course. If he'd done that it would be 3.5 million units and luckily he did not, because if he had, he'd have died undoubtedly."

Ralston said that - if the supplement had been regulated as a medicine - Roo's GP would probably have received an urgent alert.

The MHRA said the regulation of dietary supplements is the remit of the FSA and that they work together to keep the public safe.

FSS said it worked closely with the Food Standards Agency and local authorities to ensure product recalls are communicated effectively.

The Scottish government told Carys it had raised the issue of regulation and supplement recalls with the UK Department of Health and Social Care.

A month before Roo began his course of vitamin D3 drops, Kayan Khan from Sheffield had also been prescribed the same brand of supplements.

Kayan, who is now 13, was already living with several complex medical conditions including chronic kidney disease, and the eight-week course of vitamin D prescribed by his GP was in line with recommendations.

In February 2025, Kayan was admitted to hospital in Sheffield with high levels of calcium and reduced kidney function.

A letter to his mum Alaina from Sheffield Children's NHS Foundation Trust said doctors had struggled to control his calcium levels and found he had vitamin D intoxication "far above expectation for standard supplementation".

Alaina had not kept the bottle from his vitamin drops, so the exact batch could not be confirmed but the letter said that the "logical explanation" for his toxic level was a raised intake of vitamin D.

Once again, news of the FSA recall had not reached Alaina, although it had been passed on to hospital doctors and local pharmacies.

She said she only found out about the recall in April 2025.

Kayan suffered a significant deterioration in his kidney function, and although it has now recovered slightly, he may need a transplant in future.

"As a parent, as a mum, I've been let down," she said.

"I can't help but feel that for eight weeks, I'd been slowly poisoning my son."

Dr Jeff Perring, executive medical director at Sheffield Children's NHS Foundation Trust, said its standard practice was to ask GPs to prescribe medication, but that they followed strict procedures to inform patients and families about recalls of medication prescribed directly.

TriOn Pharma, the manufacturers of the drops, said that they had initiated a prompt recall and notified the FSA and the MHRA in line with requirements, after an issue was identified.

"Recall notifications were issued to all direct customers through established channels for onward communication across the supply chain," they said.

"We continue to work with authorities to support patient safety."

Roo's vitamin D levels took about a year to return to the safe range, and Carys said the long-term effects are still not clear.

"He went from an outdoor, forest school kid to someone who now needs a wheelchair to go longer distances," she said.

"He hasn't immediately gone back to who he was before and he's still dealing with that on a day to day."