Even though Paul Han hasn’t worked as a physician in more than a decade, he still vividly remembers being wrenched awake at 3 am by phone calls from patients. I’m having chest pain, they would say – and, with little else to go on, Han had to advise them on what to do next. Should they go to the emergency room or wait until morning for a regular appointment? If they did go to the ER, were they safe to drive? Would they need an ambulance? Above all, how dire was this?

Han would lie in bed deliberating the options in his head. ‘I’m going to sleep better if I send them to the emergency room,’ he says now, ‘but I know that I’m using resources, it’s inconveniencing everyone, and it may be all for nothing.’ He sometimes lost sleep fretting about the consequences of his eventual decision, calling patients back hours later to make sure they were all right.

Uncertain situations like this are far from rare in clinical practice, where doctors like Han are up against ambiguous symptoms and unpredictable treatments every day. Because medical knowledge is incomplete and constantly evolving, clinical work is often more about testing hypotheses than nailing down a definitive answer. ‘There’s nothing magical about most diagnoses,’ explains Jonathan Ilgen, who researches medical uncertainty at the University of Washington in Seattle. Of course, Ilgen says, some diagnoses, such as viral infections, can be definitively established through testing – but clinical diagnoses, which doctors determine by collating data from various sources, are more ‘socially generated hypotheses’ than anything else.

What Han found strange, however, was how no one around him ever talked about this pervasive uncertainty. His training didn’t touch on the nerve-wracking moments where Han would have no idea what to tell a patient; instead, he was forced to come up with his own strategies, such as a personal rule saying that, if he would stay up all night stressed about a patient, he should send them to the ER. Meanwhile, Han’s fellow physicians presented themselves as experts who never hesitated; faced with uncertainty, they seemed to issue decisions and emotionally disengage.

‘We have a notion of uncertainty as being synonymous with weakness or inertia,’ says the journalist Maggie Jackson, author of Uncertain: The Wisdom and Wonder of Being Unsure (2023). Studies show that people tend to evaluate leaders more positively when those leaders make faster decisions, even though taking time to think through an issue may lead to better outcomes. As the authorities of the medical field, physicians may worry that revealing their uncertainties will expose them as professionally incompetent.

Meanwhile, patients often ask for instant fixes. Han remembers some who demanded antibiotics for vague ailments, like sore throats or sinus pain. ‘What they really want,’ he says, ‘is certainty that they’re going to get better’ – but because certainty wasn’t something Han could provide, he ended up caught between upsetting his patients and prescribing drugs that were likely unnecessary.

The fact that the medical system is designed to be efficient, with split-second appointment windows that rarely allow more than a brief exchange, makes it only harder for doctors to think deeply about uncertain cases. As a primary care physician, Han used to arrive in the morning to find a roster of some 30 patients to meet with over the next few hours. ‘I didn’t have the time to dwell on anything,’ he explains. ‘You’re always moving.’

As John D Halamka and Paul Cerrato, digital healthcare experts at the Mayo Clinic in Minnesota, write in their book Transform: Mayo Clinic Platform and the Digital Future of Health (2025), doctors tend to operate by following ‘disease scripts’ based on recognisable symptom clusters. This habit-driven way of thinking, known as routine expertise, is useful for carrying out standard procedures on limited time. However, physicians falter when confronted with patients whose symptoms don’t fall within the boundaries of existing medical knowledge.

Doctors cut off any search for answers after tests failed to show obvious proof of disease

Meghan O’Rourke is one of these patients. ‘My narrative is not a neat one,’ she writes in her memoir, The Invisible Kingdom (2023). O’Rourke’s illness began so gradually that she can’t say for sure what the original symptom even was, though she opens her book by describing how, in her early 20s, she started experiencing electric shock sensations that felt ‘as if I were being stung by tiny bees.’ These evolved into a collection of vague, roaming symptoms – vertigo, night sweats, fatigue – all of which seemed to come and go at random. ‘I didn’t even connect all the symptoms initially,’ O’Rourke told me in an interview. Her early appointments centred around only whichever symptom was most relevant to each physician’s speciality; and when her tests came back inconclusive, O’Rourke’s doctors looked at the young, physically fit woman in front of them and promised that she had nothing to worry about. She wasn’t ill, they said: just tired, anxious, getting her period.

‘There was no real attempt to figure out what might be going on,’ says O’Rourke. This streak of futile appointments lasted until her early 30s, when O’Rourke’s body became so weighed down by fatigue that she could no longer make her way around the block. ‘Tired isn’t the right word,’ she explains. ‘It felt like my cells had no energy.’ One day, driving a colleague home, she glanced over and realised she had no memory of who the person in her passenger’s seat even was.

‘At that point, I sort of went on a quest to find a doctor who would help me,’ says O’Rourke. This seemed promising at first – she was diagnosed with Hashimoto’s thyroiditis, an autoimmune disease where the immune system mistakenly attacks the thyroid – but her relief waned when treatments made barely a dent in her symptoms, shoving her back into an endless loop of symptoms and dismissal.

After connecting with other patients online, O’Rourke realised her experience was disturbingly common. Countless others reported that,........

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