Our circadian rhythms have a far greater effect on our health than simply jet-lag: They regulate hormones, body temperatures, hunger and many metabolic processes. Also conditions like depression, diabetes, heart disease and Alzheimer's have a connection to your body clock.

Each person's internal clock runs on a unique schedule called chronotype. People with different chronotypes have different metabolic responses at different times of the day, and that can affect how well medicine works.

Now a new study published in the Proceedings of the National Academy of Sciences details how a blood test called TimeSignature can show a person's biological time within a 90-minute window.

TimeSignature works by analysing 41 genes from a blood sample, and finding patterns by looking at when certain proteins are created. Time of day can be extrapolated backwards from what's known about when those proteins are typically created.

This information has immediate import — doctors can be much more precise about when they administer drugs. By giving them at the right time for the body's natural cycles, lower doses of medicine can be used to get the same effect, and side-effects can be minimised.