A host of companies now offer tests, typically costing hundreds of dollars, to calculate genetic risks for common conditions like cancer, diabetes and heart disease that involve multiple genes.
But Christine Patch, a genetic counselor at Guy's and St Thomas' NHS Foundation Trust and a member of Britain's Human Genetics Commission, said most had little clinical relevance.
"My message is you are wasting your money," she told a news briefing.
People also faced either unnecessary anxiety, if a test showed a raised risk, or false reassurance, if they were given an all-clear, she added.
Paul Pharoah, from the Cancer Research UK department of oncology at Cambridge University, said real strides were being made in science but researchers still did not know enough about enough genes for tests to be really useful.
Scientists have linked a growing number of genes to common diseases but these genes typically interact... see more