A simple blood test could help predict how long you are going to live, new research suggests.
Researchers have successfully measured the speed of ageing in wild birds, opening up the possibility of doing the same for humans.
The test allows you to look at the "biological age" of individuals and also accurately predict, major illness aside, their lifespan.
The test measures the average length of tiny structures called telomeres, which are known to get shorter each time a cell divides during an organism's lifetime.
The length of telomeres provide a more accurate estimate of a person's true biological age rather than their actual chronological age.
This has led some experts to suggest that telomere tests could be used to estimate how long they have left to live, assuming they die of natural causes.
At least one company is offering a £400 blood test in the UK for people interested in seeing how fast they are ageing based on their average telomere length.
Telomere tests have been widely used on animals in experiments, now scientists have performed them on an isolated population of songbirds in the Seychelles, the Independent has reported.
"We saw that telomere length is a better indicator of life expectancy than chronological age," said David Richardson, of the University of East Anglia.
"So by measuring telomere length we have a way of estimating the biological age of an individual - how much of its life it has used up,"
The researchers tested the average telomere lengths of a population of 320 Seychelles warblers on Cousin Island, which ornithologists have studied for 20 years.
"Our results provide the first clear and unambiguous evidence of a relationship between telomere length and mortality in the wild, and substantiate the prediction that telomere length and shortening rate can act as an indicator of biological age further to chronological age," says the study, published in the journal Molecular Ecology.
Dr Richardson said: "We investigated whether, at any given age, their telomere lengths could predict imminent death.
"We found that short and rapidly shortening telomeres were a good indication that the bird would die within a year.
"We also found that individuals with longer telomeres had longer lifespans overall.
"However while telomeres do shorten with chronological age, the rate at which this happens differs between individuals of the same age.
"This is because individuals experience different amounts of biological stress due to the challenges and exertions they face in life. Telomere length can be used as a measure of the amount of damage an individual has accumulated over its life."
Telomeres are often said to be to chromosomes what plastic tips are to shoelaces.
As we age they get shorter and more ragged and lead to damage to the chromosome and DNA.