I have a turtle living in a tank inside. It recently stopped eating and acts sluggish. Is it hibernating?
You could be right BUT turtles kept indoors at normal room temperatures can not properly hibernate! When turtles do not receive 12-14 hours of light per day, hibernation mode can be triggered and your turtle will stop eating and become less active.
To properly hibernate (brumate) a turtle must have temperatures under 55 degrees. Temperatures above 55 but below 75 degrees or so, allow a turtles metabolism to slow down enough that it does not want to eat but is still high enough to use up stored energy. Basically, a turtle in this unnatural situation is starving. They can live a long time like this but chances are they will develop major organ damage and eventually die.
Sometimes respiratory infections start first and if not recognized early can cause death.
Turtles (unless it is an exotic species that is not supposed to hibernate) should be housed outside year round and allowed to hibernate naturally under normal conditions. Some species that are not native to your area or have been ill recently may need to be housed indoors over the winter. Otherwise, turtles need to be outside. Any turtle wintered over indoors needs 12-14 hours of light per day and have a warm basking area. See our page on Wintering Over Turtles Indoors.
Read more about turtles kept inside and hibernation HERE.