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Reading graphs

Same Medication, a Different Curve on a Different Day

Once you overlay the two days' curves, "today felt a bit different" turns into exactly what time it was different, and by how much.

The graph

Example curves from two different days, taking the same medication at the same times The horizontal axis runs from 06:00 to 15:00. The vertical axis is how well the body is moving, relative to that person's own range — higher is better movement. Two days with the same dose times are drawn on top of each other: March 12 and March 15. Doses are marked at 07:00, 11:00. The highest point is around 12:15. higher lower 07:00 11:00 06 08 10 12 14 Example curves from two different days, taking the same medication at the same times The horizontal axis runs from 06:00 to 15:00. The vertical axis is how well the body is moving, relative to that person's own range — higher is better movement. Two days with the same dose times are drawn on top of each other: March 12 and March 15. Doses are marked at 07:00, 11:00. The highest point is around 12:15. higher lower 07:00 11:00 06 08 10 12 14
  • March 12
  • March 15
  • Time a dose was taken (same on both days)
An example curve made for teaching. Neither line is a baseline, and actual curves vary from person to person.

If you keep records for a few days, you’re bound to run into this question. “I took the same medication at the same time — so why is it different day to day?”

The graph above draws that situation exactly as it happens. The dosing times on the two days are identical. But the first dose shows a big difference between the two curves — one rose early and climbed high, while the other didn’t rise until much later and stopped at about half that height. The second dose, on the other hand, shows the two curves nearly overlapping.

There are three things to read in this graph.

First, being different from day to day isn’t strange. The conditions that affect absorption shift a little every day, and the curve simply shows that.

Second, not every dose of the day differs equally. Some doses show a wide gap, and others are nearly identical. So saying “my medication isn’t working well these days” is much less accurate than saying “my morning dose varies a lot from day to day.”

Third, neither curve is the baseline. The two lines in the graph above aren’t normal and abnormal — they’re just two different days. That’s why this site draws both days in the same color and separates them only by a solid line and a dashed line. Drawing one of them in a faded color would make that day look like it was wrong.

Memory alone can’t make this comparison. You remember that one day was good and another was bad, but you don’t remember what time it changed and by how much. With a few days of records on hand, laying two days side by side is enough to answer that question.

What to look at

  • Whether the dose markers land in the same place on both days Check this first. If the dosing times differ, the rest of the comparison loses its meaning.
  • The horizontal gap at the point where the curve starts to rise How far apart the two curves are when they leave the bottom.
  • The vertical gap at the peak How much the peak height differs for the same dose.
  • Which doses show a big difference and which show a small one Not every dose of the day differs equally. What matters is which dose the gap shows up at.
  • The point where the two curves meet again Whether a late start still ends up about the same, or the gap stays open the whole way.

Worth recording when you see this shape

  • The dosing time on both days Before you can overlay the two days, you need to confirm the dosing times were actually the same.
  • The time the rise started on both days This is the value that creates the horizontal gap.
  • The peak and its output on both days This is the value that creates the vertical gap.
  • What was different on the day that was different Jot down even one line about meals, sleep, activity level, or how you were feeling that day.
  • How often a day like this happens Whether it's occasional or close to half the time changes the story.

The shape of the curve is material for describing your situation. Decisions about the type, dose, or timing of medication belong with the clinicians who look after you.

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