The daily fear of running out of attention deficit hyperactivity disorder (ADHD) medication feels like a "doomsday clock", according to one man.
Ryan Hendry, 30, has been affected by medication shortages and told the BBC he has about two weeks' supply left.
The Department of Health (DoH) said the UK-wide disruption should be resolved by September.
But consultant paediatrician Dr Matthew McConkey said the shortages are having a "profound effect" on patients.
Ryan said that every morning when he takes his medication it is like a "doomsday clock" is counting down the days until he will run out.
"You go seven days left, six days left, five days left, this is time to panic.
"Four days left, franticness. Two days left, every panic button has been pressed."
Ryan has been dealing with the shortages for around seven months.
He works full time and said he and his partner "can't just pause our lives running about" trying to get medication.
'Isolating and frustrating'
Ryan said that pharmacies he has spoken to don't know when they will get the medication in.
"It's scary because I don't know what happens if I go over that cliff edge," he said.
"It's incredibly isolating and frustrating."
ADHD isn't taken seriously, Ryan believes, and "there's an attitude of 'it's just naughty children, it can be managed, these tablets aren't really needed'".
However he has been on stimulants to deal with his ADHD for almost 20 years and stressed that once you find the right medication "it's important that supply is maintained".
"On days I haven't taken them I feel extremely agitated, panicky and it's almost short-term memory loss," he said.
"I go to make myself a cup of tea and come back a few hours later in the kitchen there will be a cup with teabag and a boiled kettle but I won't have made a cup of tea."
Other effects of stopping medication include mental fatigue and migraines, with symptoms worsening as time passes.
"Hospitalisation would be a real possibility - my dosage is quite high and NHS guidelines says sudden withdrawal is to be avoided."
What is ADHD?
ADHD is a neurodevelopmental condition that can cause memory issues, problems concentrating, focusing or sitting still.
According to the NHS, people with ADHD can seem restless, may have trouble concentrating and may be impulsive.
Most cases are diagnosed in childhood, but the UK-wide ADHD Foundation said it has seen a 400% rise in adults going to them compared to before the Covid-19 pandemic.
What medication is available for ADHD?
There are four different ADHD medications available which fall into two categories - stimulants and non-stimulants - with most people taking stimulants.
Reasons for the shortages, according to Dr McConkey, include an increase in global demand for the medication and manufacturing issues.
While Dr McConkey works with children, he said he is also aware of the impact of the shortages on adults.
"I've heard of some adults asking their bosses to make reasonable adaptations because of the fact they aren't having access to medication and in some cases those people have lost their jobs," he said.
"So it has very profound effects on people who don't have access to medication that was doing them a huge benefit."
For Dr McConkey's patients, who are predominantly under 18, not taking medication affects their schooling, exam preparation, exam performance and mental health.
"It can cause anxiety, it can cause low self-esteem, and more flashpoints with family, friends and schools, colleagues," he said.
Dr McConkey added that mortality for people with ADHD is twice that of the general population.
"If you are a young driver there is an increased risk of accidents without medication. There is a risk of substantial mood disorder.
"I am contacted daily by parents at their wits' end trying to source medication for their child."
'Light at the end of the tunnel'
However Dr McConkey said he had conversations with some pharmacists last week who said that at least one medication shortage has ended - so he feels there is now "light at the end of the tunnel".
The DoH said that while supply disruptions of some ADHD treatments have now been resolved, there are "some ongoing disruptions across the UK affecting various preparations and strengths of these medicines".
The spokesperson added: "Currently, the anticipated resupply dates of products affected by these disruptions are expected to resolve between May and September 2024, depending on the strength and preparation affected.
"Guidance, which has been agreed by the UK administrations, has been issued to healthcare professionals in Northern Ireland addressing the medicines affected by these disruptions."