Normal Is a Range

Many patients, after hearing the whole explanation, ask this right before standing up to leave.

"So why exactly does this medicine matter for my condition?"

I have thought about this question for a long time. I have written many pieces about what happens in the body, and about what a test can and cannot see. But something remains after all that. So then, what am I going to do about it, and how?

This piece is written to answer that question. To do so, there is something I need to lay out first. What is normal?

The Body Does Not Hold a Single Number

Picture someone standing on a balance beam. Someone doing it well looks as though they are standing still. But in fact, their body is constantly tilting left and right and returning, over and over. They are not staying upright because they never sway — they are staying upright because they return every time they sway.

The body's regulation works the same way.

People say body temperature is fixed exactly at 36.5°C, but actual body temperature rises and falls over the course of a day, and the very benchmark the body maintains shifts from one period to another. The same is true of blood sugar, blood pressure, and hormones. They are not held exactly in place — they rise and fall while staying within a certain range.

There is a reason it has to be this way. The body cannot regulate itself the way a computer switches things on and off. There are simply too many cells making up the body, and issuing a command to all of them at once is impossible. So the body regulates by direction and speed — this way, this fast. As a result, values overshoot the target and fall short of it in turn, tracing a wave as they rise and fall.

That is why normal is not a point but a range. It is not fixed by a single number.

Then What Is Illness?

A value briefly moving outside its range happens all the time. Climbing stairs raises the heart rate; eating a meal raises blood sugar. We do not call that illness, because it returns soon after.

The problem I mostly look for is a place where the strength to return, once it has moved outside the range, has weakened.

Tilting on the balance beam is not, in itself, the problem. You fall when you tilt and cannot return. The body is the same. Rather than the rising and falling itself, what matters just as much is how well it returns after moving outside its range.

This power to return — resilience — is the axis of my practice. Think of a rubber band: not the property of stretching, but the property of snapping back into place once released.

But That Range Is Not Fixed

It differs from person to person. The same number falls within range for one person and outside it for another. Each person maintains a different benchmark. When four thyroid-related values were measured repeatedly in healthy people, the range within which each individual's values rose and fell was only half as wide as the range used as the population benchmark — so a value can sit inside the population's normal range and still be abnormal for that particular person.

It differs from time to time. The range changes with age, with hormones, with the season, with the condition of the day.

And it keeps shifting. It is not set once and left fixed.

When discussing a child's body, I often say that an adult's ruler cannot simply be applied. Even within the same child, the benchmark changes between one year and the next. I discussed this in What the ‘Normal Range’ on a Checkup Result Actually Means. This is not something unique to children. In an adult body too, the range keeps shifting.

The body has a capacity called adaptation. When the same stimulus repeats for a long time, the body changes itself to accommodate it. This shows up especially clearly in the nervous system and the immune system. Staying awake and working at night is not naturally normal, yet there really are people who have worked night shifts for over twenty years without any real trouble. The body has widened its range to fit that way of life.

One patient asked me this. For nearly thirty years, because of work, they had eaten their first meal in the late afternoon and their next meal late at night. They asked whether it was all right to keep living this way.

Having held to that interval for so long means the body had adapted to it to some degree.

But then they added something. They said hunger had become harder to bear lately than it used to be.

This is where the story changes.

Adaptation is not evolution. The body's underlying makeup has not changed; it has only widened the range it can tolerate. So when the strength to maintain that range weakens, the situation changes.

As people age, the capacity to store energy and draw on it declines little by little. Storing sugar as glycogen in the liver, and releasing it when needed, are no longer what they used to be. The loss of muscle mass adds to this. Muscle is not only where force is generated but also a storehouse where energy is kept, so when muscle declines, the storehouse shrinks.

The lifestyle has stayed the same, but the storehouse has shrunk. Enduring for thirty years was possible because the storehouse was ample; now that it has shrunk, the same interval feels longer. The same thing feels different, and the body responds differently.

So this is what I tell patients. You have to respond according to the state of the body. You have to listen to what the body is telling you, and adjust accordingly.

This is not telling you to drop that habit right away, nor is it telling you it is fine to keep going as before. It means looking at how far this body can go right now and adjusting to that. There is no rule that what worked yesterday will work today, nor any rule that what does not work today will not work tomorrow either.

I say the same thing when it comes to exercise.

It is easy to assume that since it is good for the body, more of it must be better. But a great many patients come to my clinic after running into trouble from overdoing exercise. There is a goal they have set their mind to, a volume they used to be able to handle, and they push today's body to keep meeting it. This is not only about exercise. It is the same with mealtimes, sleep times, and the order of the day.

Rather than pushing forward on willpower and a fixed goal, it is better to adjust to the body's current condition, I tell my patients. This does not mean doing more, nor does it mean doing less. It means adjusting. On a day when the range is wide, use it to the extent it is wide; on a day when it has narrowed, use it to the extent it has narrowed. Doing so is, in the end, also the way to protect that range.

What I Do in My Clinic, Then

Seen this way, what I do becomes clear.

Finding the point at which the body is failing to return.

Even the same headache stalls at a different point for different people. For one patient, pressure at the epigastrium is pressing on the diaphragm; for another, signals from the gut keep rising; for another, the body is swinging up and down too abruptly. The symptom's name may be the same, but the spot to address is different. Conversely, two symptoms that go by different names can sometimes branch off from the same single place.

So I do not chase the name of a symptom alone. I look, together with it, at the conditions that are producing it.

How Herbal Medicine Does That Work

A symptom that cannot be explained by a single value does not have a single spot to address, either. I examine several conditions together and find which one carries the greater share for this particular person right now.

Herbal medicine is prescribed in keeping with that judgment. I make use of the fact that its many components act on different sites and at different times, but I do not fix the same direction of treatment for every person. The work of returning is done by the body; what I look for is how to reduce the conditions that are getting in its way.

This matches exactly what I actually do in practice. For a patient whose nerves have become sensitized, I do not go only toward suppressing and quieting the nerve. I look first for where it is that keeps irritating that nerve. Once that spot is released, the signal settles down on its own.

Why I Bother Writing This

There are many practitioners better at treating patients than I am, and many who see far more patients than I do.

But I believe that someone has to put forward a perspective and a framework for those walking the same path to be able to move forward together, one step at a time. And only then can practitioners of conventional medicine understand what Korean medicine is actually looking at. Even using different vocabularies, I think we should be able to convey to each other what it is we are seeing.

That is why I do not disclose specific prescriptions. Medicine is prescribed differently for each person, and it is not something that can be put into writing that way. Instead, I tell you what I look at and where I put my hand. I believe that kind of account grows more valuable the more it is shared.

Back to the Question I Started With

"So why exactly does this medicine matter for my condition?"

Now I answer it this way.

It is not a matter of looking only at the body's current numbers. You have to look at why those numbers are shaking, and what conditions are slowing recovery. I aim at the conditions I can actually confirm.

The pieces that follow usually start from a single symptom. But they are all telling the same story: what conditions lie together behind that name.

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When the body has suddenly changed — a symptom appears out of nowhere that was never there before, it does not settle even with rest, it wakes you at night, or fever or weight change comes along with it — it is better to get tested first. Before talking about the strength of return, you first need to check whether there is a disease or injury that needs treating.

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)