After years of being unable to sleep, I took this popular supplement and had the best night’s rest of my life… until I woke up with heart palpitations and was rushed to hospital. Don’t make my mistake

After years of sleepless nights that were getting progressively worse, Dale Allen was desperate.

Struggling by on only ‘a couple of hours a night in total’, Dale, who runs a safety software company, recalls: ‘I’d go to sleep at 9pm, wake at 11pm – then stay awake all night.

‘I was exhausted and gained weight. I had energy crashes and anxiety throughout the day.’

So when an online health coach suggested taking a ‘sleep stack’ of supplements to help him drop off, he thought he had nothing to lose.

‘As a business owner and content creator I needed energy to focus,’ he says. ‘Sleep was crucial.’

So he ordered the sleep stack – a bundle of supplements containing magnesium bisglycinate (1,000mg), zinc (30mg), 5-HTP (25mg) and melatonin (3mg), which is often referred to as the sleep hormone – from a website based in the US.

At first Dale was delighted with the tablets that arrived in the post.

‘I took the first dose of just melatonin – one 3mg tablet – that night as instructed and it worked,’ says Dale, 44, from Chorley, Lancashire, who is married to Czarina, 32 and has three children aged nine, eight and five.

‘I slept like a brick immediately. It was the first night in years I’d slept through.’

Desperate to get a second good night’s sleep, he took another pill. But this time he woke early the next morning with severe heart palpitations.

‘I felt like my heart belonged to somebody else,’ recalls Dale. ‘I was terrified; it just kept racing up and then dropping so low it felt like it was barely beating, then surging back up again. It got faster and more erratic, and I didn’t know what was happening. I genuinely thought my heart was going to go “Pop!”.

‘My heart was pounding out of control, with waves of fear and adrenaline flooding my body, while I was fully conscious but unable to stop it.’

His sports watch indicated his heart rate was 100 beats per minute (bpm), ‘even though I was lying down’, he says. ‘My normal resting heart rate was about 47 bpm.’

So Dale drove himself to his local urgent care clinic, where medics performed an electrocardiogram (ECG) to measure his heart rate and rhythm.

On seeing the results, a clearly anxious doctor called for an ambulance to transfer Dale to Royal Preston Hospital.

‘By the time the ambulance arrived, my heart rate had hit 205 bpm,’ says Dale.

There, Dale was given an echocardiogram – which produces a detailed scan of the heart – and he was kept in overnight for monitoring.

He told the doctors about the melatonin, but they didn’t think it had caused his symptoms. He was allowed home the next day.

Although he dismissed the incident as a ‘silly, one-off blip’, Dale nonetheless stopped taking the sleep stack tablets – and also the testosterone he’d bought online and had been taking for three weeks on the recommendation of the health coach.

But his sleep problems returned so, after a month, he took just the melatonin.

Next morning, Dale’s heart was beating wildly again, so he rushed back to hospital: after another ECG he was told he’d developed an irregular and rapid heartbeat.

‘The doctor prescribed propranolol [a beta blocker] to help manage what he thought was anxiety and to prevent further attacks,’ Dale says.

‘They told me to stop taking melatonin immediately. I felt so stupid for taking it again.’ He was kept in hospital overnight while his heart rate settled.

Melatonin is a hormone naturally produced by the pineal gland in the brain in increasing amounts as darkness falls, to signal to your body that it’s time to sleep.

In the UK melatonin is a prescription-only medicine and its use is limited, mainly to adults aged over 55, or children aged six to 17 with insomnia and attention deficit hyperactivity disorder (ADHD) or delayed sleep-wake phase disorder (DSWPD). Prescription doses are 2-3mg.

You can, however, buy supplements online – as Dale did.

While the NHS says ‘it does not have many common side effects’, a recent study has raised concerns around melatonin’s effect on heart health.

Earlier this month a US study, presented at the American Heart Association conference and based on the health records of 130,000 adults who were prescribed melatonin for insomnia, found they were more likely to be diagnosed with heart failure, require hospitalisation or die from any cause.

However, the study had not undergone peer review, points out Dr Ricardo Petraco, a consultant cardiologist at Imperial College Healthcare NHS Trust and the Mayo Clinic, both in London.

He adds: ‘This study was purely observational and involved a retrospective review of five years’ worth of medical records. Crucially, it was not a prospective clinical trial with a control group.’

In other words, it doesn’t prove that melatonin use caused heart problems.

‘Patients prescribed melatonin may have had more severe insomnia or other underlying health issues, which could confound the results,’ adds Dr Petraco.

There have ‘been rare case reports of ventricular arrhythmias – dangerous heart rhythms – in individuals with structurally normal hearts taking melatonin’, he adds. ‘However, these are isolated cases, and the data does not support a direct causal link.’

In general, side effects of melatonin are mild and infrequent.

‘Patients often report palpitations, but these typically resolve after discontinuation,’ says Dr Petraco.

However, patients with a history of significant heart-rhythm problems – or those with cardiac devices, such as defibrillator implants – should consult their healthcare providers before using melatonin, he adds.

He also recommends sticking to usual doses (2mg-10mg), using the supplement for a short duration when possible, and discussing any concerns with a medical professional.

‘While current evidence does not indicate a significant risk of melatonin at typical doses, this new study underscores the importance of ongoing research,’ says Dr Petraco.

Pharmacists, meanwhile, have concerns that many people are now buying melatonin from unregulated sources online.

In the UK, melatonin can be prescribed by trusted, regulated online pharmacies, but only after the patient completes a short medical assessment – the information provided is then reviewed by a qualified prescriber, who decides whether a prescription can be issued in line with UK regulations.

Umar Razzaq, co-founder of Pharmacy Online, warns that unregulated melatonin bought online will not adhere to the standard dose of prescribed melatonin.

What’s more, he says, many factors can influence the effect melatonin has on the body.

Melatonin is broken down in the liver by an enzyme, CYP1A2 – but the time this process takes can vary.

For instance, smoking makes the CYP1A2 enzyme work faster, so melatonin is cleared from the body more quickly – which means that melatonin might not induce sleep as well in smokers, explains Umar Razzaq.

He adds: ‘Hormone replacement therapy (HRT), which contains oestrogen, has the opposite effect. It slows melatonin breakdown, which can increase its levels in the body and so might cause stronger or longer-lasting drowsiness.’

Too much melatonin – more than the licensed dose of 2mg daily for short-term insomnia and 3mg for jet lag – could also cause nightmares, headaches, irritability, stomach pain, nausea and dizziness.

The hormone could potentially interact with other medications, such as the antidepressant fluvoxamine, which can increase melatonin levels in the body; psoralens (compounds used to treat skin disorders such as psoriasis) and some antibiotics.

‘Rifampicin [an antibiotic used to treat serious bacterial infections] can decrease the effect of melatonin, whereas quinolones [another type of antibiotic] can increase it,’ says Umar Razzaq.

‘Melatonin can also influence the effect of the anticoagulant warfarin [boosting its effects, leading to bruising and potentially bleeding].’

This means it’s important to discuss taking melatonin with your healthcare professional before starting.

‘In my discharge letter, the consultant wrote that although at my initial consultations they’d believed my heart problems had been brought on by “black-market testosterone… Dale is probably rightly of the opinion that they were brought on by melatonin, which he had used about 48 hours before these episodes of the arrhythmia”.

‘The doctor also noted that since I had stopped melatonin, I’d had no more episodes.’

Now recovered, Dale says: ‘Don’t self-diagnose or self-medicate. Understand how interconnected your body’s systems are.

‘I’ve now ditched supplements like melatonin, and am now being treated at the Maas clinic [in West Sussex], which combines medical treatments with lifestyle and diet changes.’ He is now sleeping well.

‘I was completely naïve about supplements,’ he adds. ‘Buying melatonin online felt harmless. I now fully understand that medical supervision is essential.’