You take a painkiller, swallow it with some water and settle onto the sofa while you wait for it to work.
Most of us think the important part is what happens next: the pill breaks down, the medicine is absorbed and, eventually, the headache or backache starts to ease.
But there's another factor you probably don't think about when you swallow a pill: the position of your body.
Your stomach isn't a simple vertical bag. It's curved and angled inside your body, which means gravity can affect where a pill settles and how quickly it moves toward the small intestine.
Researchers at Johns Hopkins University wanted to find out just how much that matters. Using a detailed computer model of the human stomach, they tested what happened to a pill when the body was in four different positions.
The difference was bigger than expected
The results were striking. In the model, a pill dissolved in about 10 minutes when the body was tilted to the right.
Upright or lying on the back took around 23 minutes. On the left side, the same pill took more than 100 minutes to dissolve and move toward the small intestine.
That's a huge difference from something as simple as changing position.
The researchers found that the right-side position produced a dissolution rate about 2.3 times faster than the upright position in their model.
Why does the right side make a difference?
Your stomach has a curved shape, with its lower part leading toward the small intestine.
When you're tilted to the right, gravity helps move the pill toward this lower section. That puts it closer to the opening through which stomach contents leave and enter the small intestine.
On the left side, the opposite happens. The pill tends to remain higher in the stomach, so it takes longer to reach the exit.
That's why the researchers found such a dramatic difference between the two sides. It isn't the pill itself changing. It's where the pill ends up inside your stomach.
There's an important catch
The numbers sound impressive, but there's a reason not to start changing how you take every medication based on this study.
The researchers used StomachSim, a computer model of the human stomach. They were studying pill dissolution and the movement of the drug into the small intestine, not measuring how quickly people actually felt pain relief.
The study therefore doesn't prove that taking your painkiller on your right side will make your headache disappear faster.
And some medicines come with specific instructions about staying upright after swallowing them. For example, certain medicines can irritate the esophagus if you lie down after taking them. Your medication's label or your pharmacist's advice should always take priority.
So what should you do?
If you're taking a regular pill and there's no instruction telling you to stay upright, lying on your right side may help it move through your stomach faster.
That's the simple takeaway from the study. The effect was especially interesting for people who spend a lot of time in bed, but it may also be useful to know the next time you're waiting for a painkiller to kick in.
Just remember that not every medicine should be taken this way. Follow the instructions that come with your medication first.
Still, the finding is a good reminder that something as simple as the position you're in when you swallow a pill can make a surprising difference to what happens inside your body.