How to tell the age of a turtle? Most male turtles will have longer, thicker tails than females will to contain the male's phallus. So, research on your pet turtle species and determine how long it will take for it to be adult. In male turtles, the plastron is slightly concave while in females it is flat. This makes determining their sex much more difficult, but it's not impossible. If the underbelly does not have blue coloring, it's a female. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
But in order to reliably use shell size as a factor in determining the sex of a turtle, you must also know its age.
Is it a boy or a girl?
It is better if you have both a male and female turtle so that you can compare both and identify the gender easily. This change can be used as another indicator that a turtle is a female, but until and unless it lays eggs, appetite shouldn't be used as the sole method for determining its gender. However, I find this very unreliable as there are many female turtle species with bright red eyes. A Green turtle hatchling heads to sea in the northwest Hawaiian islands. This makes determining their sex much more difficult, but it's not impossible. Tell us more about it? If you suspect your pet is sick, call your vet immediately.