Checking if a variable is initialized

Seems like this would be a duplicate, but maybe it is just so obvious it hasn't been asked...

Is this the proper way of checking if a variable (not pointer) is initialized in a C++ class?

class MyClass
{
    void SomeMethod();

    char mCharacter;
    double mDecimal;
};

void MyClass::SomeMethod()
{
    if ( mCharacter )
    {
        // do something with mCharacter.
    }

    if ( ! mDecimal )
    {
        // define mDecimal.
    }
}