A doctor

Peter Burke, GP

Metric units are the only way forward in medicine and healthcare. That has always been my firm belief. As the years have gone by this conviction has grown. Although now in my 60s, I was taught primarily metric units at school, and I think nowadays one needs to be fairly advanced in years to have been taught otherwise.

The advantages of metric units in general use are obvious. The only multiplier one has to think of is 10, and converting between units generally speaking involves nothing more than moving a decimal point. There is a clear relationship between, for example, units of length, area, volume and mass. This comes into its own in medicine, for example, when calculating body mass index.

The use of dual units can have consequences ranging from the tragic (for example misunderstandings around the calculation of drug dosages) to the absurd, for example the often reported case of Liam Thorp, who was erroneously called in by his practice for coronavirus vaccine because the computer found him to be obese: in fact his BMI had been recorded as 28,000 (ideal: 19-25) because he had put in his height as 6 ft 2 inches where he was asked for centimetres, so the computer had him down as 6.2 cm.

Dual units are obviously undesirable and confusing, and if we’re going to settle for a single system it must be metric. Metric units have been the norm among scientists and medical professionals for the greater part of the past century. This extends to physiological measures (height, weight, peak flow, blood pressure etc.), blood results, drug dosages and even the calorific value of foods.

As a GP I find it frustrating that there are still some patients, and not all of them elderly, who when given their weight in kilograms want to know “what’s that in real money?”. Even some adults who quote their own weight in kilograms, and would never think of using anything other than grams in the kitchen, will give the birth weight of their babies in pounds and ounces. And yet for many, even educated people, it would be impossible to convert between different magnitudes of imperial units, eg they would not know how many pounds or stones there are in a ton, or how many inches in a mile, and would have to look it up. And is it not bizarre that when we’re talking about getting exercise people have no difficulty with the concept of the “couch to 5k” or running “9 minutes per kilometre”, yet as soon as they get into the car they have to switch to miles?

Of course for my many patients from outside the UK, even oddly enough the USA, talking about stones and pounds or yards and feet produces at the least a raised eyebrow.

In so many areas of medicine and science, the UK has made a contribution well out of proportion to its size. The most recent example is the development of effective and affordable coronavirus vaccines. All of this of course was done in collaboration with the international scientific community, and all, needless to say, using metric units. People have a right to be proud of these achievements, much more so than of an imperial past which is not going to return.

We are citizens of the world. Not only are metric units fit for purpose, but they are universally understood. Any steps to encourage the wider use of imperial units is an exercise in obscurantism and carries significant risks. The direction of movement should be totally the opposite. The sooner our Government realises this the better.

Dr Peter Burke comes originally from Ireland (where speed limits have been in kilometres per hour since 2005, and the transition to metric road signs was extremely smooth). He worked as a GP partner in Oxford for 27 years, and continues as an honorary senior clinical lecturer at Oxford University, where he teaches communication skills to medical students. He is also actively involved in the British Medical Association and the Royal College of General Practitioners.