When you take melatonin pills, your body only absorbs about 15% of the dose into your bloodstream because most of it gets broken down before it can circulate. This means oral supplements deliver much less active melatonin to your system compared to an injection.

This means that no matter whether you take melatonin as a pill or get it through an IV, your body clears it out at the exact same speed once it's in your blood. The way you initially get the supplement into your system doesn't change how long it stays in your body.

Taking a higher dose of melatonin might help more of the supplement actually get into your bloodstream. This happens because larger amounts can overwhelm the liver's natural breakdown process, making the supplement more effective than standard low doses.

When you swallow melatonin pills, your liver breaks down most of it before it can actually enter your bloodstream, meaning only about 2.5% of the dose actually works. Because so much is lost this way, you might need to take much higher oral doses to get the same effect as an injection.

Taking melatonin by injection results in about 110 times more of the drug in your blood compared to taking the same dose by mouth. This happens because your liver breaks down most of the oral melatonin before it reaches the rest of your body, which is why you need a much larger pill to get the same effect as a small injection.

When you take a melatonin pill, your body only absorbs about 15% of it because most of it gets broken down by your liver before it enters your bloodstream. Even so, the amount that does get absorbed can still be up to ten times more than what your body naturally makes at night.