Almost two months after Michelle Trachtenberg, an actress known for her role in “Gossip Girl” and “Buffy the Vampire Slayer,” died at 39, officials have issued a ruling on her cause of death as complications of diabetes mellitus. The manner was determined to be natural.

The New York City’s Office of Chief Medical Examiner, who determined the cause of death, previously said in February that the cause and manner were “undetermined.”

Here’s a look at what diabetes mellitus is and how complications can arise.

What is diabetes mellitus?

Diabetes mellitus is “a disease of inadequate control of blood levels of glucose,” according to the National Library of Medicine.

“It has many subclassifications, including type 1, type 2, maturity-onset diabetes of the young (MODY), gestational diabetes, neonatal diabetes, and steroid-induced diabetes. Type 1 and 2 [diabetes mellitus] are the main subtypes, each with different pathophysiology, presentation, and management, but both have a potential for hyperglycemia.”

What complications can arise from diabetes mellitus?

Diabetes can cause many complications if not treated properly. Blood glucose powers cells and when it is imbalanced can cause heart, lung and organ problems, according to the National Library of Medicine.