Our bodies and minds are in ceaseless transformation and I’ve spent the last few years writing about how that flux both sustains and lends dynamism to human life. It’s a message that can feel like a curse or a consolation: if things are going well, they won’t stay that way for long; if things are going badly hold tight – change is just around the corner. In my work as a doctor it’s the consolations I emphasise – people come to my clinic in the hope of influencing a change in their lives. That change may be modest and routine, or urgent and dramatic, but inevitably it is a perennial source of hope.

Many books have helped me navigate transformation’s personal, social and cultural territory. Some nudged me towards a more intimate understanding of those way stations of life I’ll never undergo, such as pregnancy or the menopause. For the former, I reached for Chitra Ramaswamy’s Expecting: across nine chapters she charts her burgeoning pregnancy. Of the linea nigra, the black line that develops down the front of the belly during pregnancy, she writes: “It bisected my stomach like a ring around a planet or a veined streak of quartz encircling a pebble, evidence of a disturbance within. Some mysterious ancient change.”

To understand more about the menopause I was recommended Ursula K Le Guin’s The Space Crone – the first essay in her collection Dancing at the Edge of the World: Thoughts on Words, Women, Places. It is panoramic in scope but beautifully concise. Le Guin proposed that women become more comfortable with accepting the third stage in their lives: “The woman who is willing to make that change must become pregnant with herself, at last.” Women in the third stage of life, she said, have experienced more fully what it is to be human than any other group, having “acted the entire human condition – the essential quality of which is Change”.

Changes in mental experience are another kind of transformation, from dreaming and memory to hallucination and psychosis, and mental illness may effect dramatic bodily change. Anorexia may be as baffling and frustrating for those who suffer it as it is for therapists trying to help – it has the highest death rate of any mental illness. To better comprehend its complexity I recommend Katy Waldman’s extraordinary Slate essay There Once Was a Girl. “I starved,” wrote Waldman, “to acquire that old classical capability: metamorphosis.”

Feeling uncomfortable in your birth gender is another issue that brings some to the clinic, seeking prescriptions for oestrogen or testosterone. Maggie Nelson’s poetic memoir The Argonauts points out that we are all in continuous transition, irrespective of gender: “On the inside, we were two human animals undergoing transformation beside each other, bearing each other loose witness.” She quotes her transitioning partner’s impatience with the idea that anyone taking hormones must be on a journey to one binary extreme or the other: “I’m not on my way anywhere.”

Some of the transformations I’ve been examining have been crises: cancer, hormonal imbalance, fracture, amputation. I met with Olivia Giles, who lost both hands and both feet to septicaemia, and whose charity 500 miles provides low-cost prosthetic limbs to amputees in Malawi and Zambia. Giles told me “the most transformative thing about prosthetic limbs is the potential they offer for children. You can see it in the mothers’ faces when the new limbs are fitted; they know their child has a future.”

And transformation is one of the most ancient and resonant themes in literature and art: two thousand years ago in Metamorphoses, the Latin poet Ovid painted nature and mankind as a seething maelstrom of flux. Marina Warner’s Fantastic Metamorphoses, Other Worlds maps this cultural topography since Ovid, showing how stories of change can guide us through the perils of life. “It would be stupid to suggest stories invariably enlighten,” Warner says, “but stories do offer a way of imagining alternatives, mapping possibilities, exciting hope, warding off danger by forestalling it, casting spells of order on the unknown ahead.” At its best, the same could be said of medicine.

• Gavin Francis will discuss his book Shapeshifters: On Medicine & Human Change (Wellcome) at the Hay festival on Monday 28 May. hayfestival.com.