With the possibility of a no-deal Brexit two months away, one 26-year-old has started stockpiling her diabetes medication in case of shortages.
Rebecca [not her real name], who has type 1 diabetes, has put aside six months' worth of her drugs.
But the Welsh Government said individual stockpiling creates an "unnecessary pressure" on the system.
The Department of Health said it had stockpiled six weeks' worth of drugs for the public in a contingency plan.
'Only so much room in my fridge'
Rebecca, a civil servant from Carmarthenshire who asked to remain anonymous, is concerned her diabetes will be mismanaged by the effects of a no-deal.
She said all of her drugs, produced by European drugs companies, could be at risk of disruption at UK borders in March.
"I am going to die if I don't have the right insulin - it may sound silly to someone who doesn't have it," she said.
"I am keeping a month back each time I get my prescription, but I have only got so much room in my fridge."
Rebecca added that she was worried her condition would be affected if food prices rise, after retailers warned a no-deal Brexit threatens the UK's food security.
"I can't eat processed food because of the amount of added sugar, so I have to eat more fruit and vegetables," she said.
But the Welsh Government's chief pharmaceutical officer, Andrew Evans, said people stockpiling for themselves might prevent someone else from getting the medicines they need.
"There is absolutely no need for people to stockpile," Mr Evans said.
"Stockpiling is unnecessary and could compromise the plans being implemented by the UK government, reducing the availability of medicines for patients in other areas of Wales or the UK."
'Dog eat dog'
Karen MacIntyre Huws, 43 from Clynnog Fawr in Gwynedd, also has type 1 diabetes - and said she is putting aside more of her medication, calling it a "life and death situation".
She added: "People need water, food, oxygen to live. I require a substance called insulin.
"You could call me a bit of a squirrel maybe, I'm just being more careful until I am offered more reassurance."
She said her human synthetic insulin is produced in Denmark and not in the UK, and that she "depends on this medicine to live."
"It is very much dog eat dog... I just remember the standstill that Britain came to with foot and mouth in 2001, there was no fuel supplies, milk, you were rationed and limited so if something as simple as foot and mouth can bring the country to a halt, something as big as Brexit is sure to have the same effect.
"I depend on this medicine to live. It's serious. It's a dire situation that I'm faced with."
A report by Public Health Wales on the health impacts of Brexit said there was "significant uncertainty" over the mechanisms and standards for the regulation of medicines post-Brexit.
'They are playing with my health'
Meanwhile, Dan Schmeising, 23, who takes medication for his epilepsy, said he was "increasingly worried" about running out of medication, if there is a no-deal Brexit.
"I don't blame people in this situation who have ordered extra for themselves," he said.
But if people start creating their own stockpiles it will deplete the main supply, according to the chair of the Royal Pharmaceutical Society in Wales, Suzanne Scott-Thomas.
"Our advice to patients is to continue their medication orders as they are usually prescribed.
"If you have any concerns about your medications, talk to your community pharmacist or practice pharmacist," Ms Scott-Thomas said.