The U.S. Food and Drug Administration has been casting a wary eye on genetic test kits that tout their ability to dissect the risks you might carry for various diseases in your DNA. But are customers getting a fair portrait of their health?

After receiving a stern warning letter from the FDA, 23andMe – the testing service backed by Google – said in early December that it would discontinue its health screening service. (Users can still get “raw genetic data” and ancestry analyses, though.)

DNA-based health analyses like the kind (formerly) sold by 23andMe and other companies look for particular little markers in a person’s DNA called single nucleotide polymorphisms. These are places where a single letter in the genetic code is different. SNPs are everywhere in our genomes, often signifying nothing, but some certain variations have been linked to certain diseases.

The problem, critics say, is that commercial tests will look for just a few SNPs to determine disease risk, when there are many other factors that contribute to your chance of developing disease. For instance, 23andMe used to look for three particular SNPs in the breast cancer-related genes BRCA1 and BRCA2 to determine a customer’s breast cancer risk.

But “that's just such a limited view of breast cancer genetics," genetic counselor Amy Strum told LiveScience in November.

Other genes besides BRCA1 and BRCA2 have been linked to breast cancer, and it may take the combination of hundreds or even thousands of genetic markers to influence breast cancer risk, according to LiveScience.

Also, different genetic tests may give consumers different results. New York Times reporter Kira Peikoff recently decided to compare three genetic testing kits: a $99 saliva test from 23andMe (she got hers before the FDA hammer came down); a $285 blood test from Genetic Testing Laboratories; and a $399 kit from Pathway Genomics.

“I set out to test the tests,” Peikoff wrote. “Could three of them agree on me?”

Short answer: no. The 23andMe test showed that Peikoff’s most elevated health risks were for psoriasis and rheumatoid arthritis, while Genetic Testing Laboratories found the exact opposite, saying her lowest risks were for those same two conditions. The various companies also use no standard language for conveying risk: a 10.3 percent risk for type 2 diabetes was deemed “medium” by G.T.L., while 23andMe dubs a 15.7 percent risk for the condition “decreased.”

Additionally, with some conditions like type 2 diabetes, genetics is only a small portion of the picture. Scientists know that family history, environment, and lifestyle choices matter in diabetes – factors that fall outside the realm of a home DNA spit test.

“What you look like is almost 100 percent genetic, but what you’re going to get isn’t,” University of Iowa geneticist Jeffrey Murray told the Washington Post this past April. “There are lots of other things — random chance, environmental exposure and all kinds of stuff that we can’t control.”