The first genetic test available to determine a risk factor for type 2 diabetes recently became available. I just beta tested and discussed it with the company’s CEO and several other officials. DNA Direct, a privately funded company in San Francisco, offers the test of this gene that can lead to diabetes.

An Icelandic company named deCode Genetics discovered the gene. DNA Direct has a contractual relationship with deCode.

The name of this gene variant is the transcription factor 7-like 2 gene (TCF7L2), which is too difficult to remember. So it goes by the nickname “deCode T2” or simply “TT.”

The test works, so it passed my beta test. You might say, however, that I failed it, because the test show that I am genetically at risk of having diabetes by carrying two copies of the variant.

No big surprise here, because ever since 1994 I’ve known that I have diabetes. And I don’t feel that I failed, because it gave me knowledge about who I am, in the same sense that my genealogical research on my family helped me understand my origin.

If I were planning on raising a family, this knowledge would be even more important. If I were married and if my wife also tested positive for the diabetes gene, we might think twice about having children. When both parents have two copies each of diabetes gene, their children are at a greater risk than when one parent has it.

But there may be a more immediate reason why you would want to know if you, like me, test positive for this gene. I picked up my first hint from Clyde Shores, deCode’s vice president for diagnostic marketing and sales when we met at the American Diabetes Association’s June scientific sessions in Chicago. All he would say then was that some people have lower response rates to some diabetes drug if they test positive for this gene.

The second hint is on DNA Direct’s website. It says there that, “It can also help your doctor to determine the most effective treatment.”

Until I talked with DNA Direct’s CEO Ryan Phelan and three company officials this week I kept wondering if they had anything specifically in mind. They certainly do. Their studies show that sulfonylureas – perhaps the most common diabetes drug – might not be as effect for people who, like me, are positive for the diabetes T2 gene.

“Some of them do respond to a sulfonylurea,” says Lisa Lee, director of content development, “but not as many as respond to metformin or who are negative for the TT gene. They are less likely to be able to reach a normal A1C level from being on a sulfonylurea compared with people who are negative for the gene or on metformin.”

If you have type 2 diabetes, you are more likely to test positive for this gene variant than people who don’t have type 2. Technically, that means carrying the risk variant for the TCF7L2 gene on both chromosomes. If you don’t have this gene at all or even if you have only one copy of it, you don’t have this genetic risk of diabetes.