Yes, there have been warnings about Invokana. In 2018, the Food and Drug Administration (FDA) warned the public about an increased risk of Fournier’s gangrene for those who take SGLT2 inhibitors. In 2019, the FDA required that Invokana carry a “black box” label to draw consumers’ attention to serious or life-threatening risks associated with the drug. This is the most serious warning that the FDA requires.