What's the difference between low self esteem and narcissism?

Self esteem. You can have low self esteem without being narcissistic, although they can occur together as well. Best.
Low esteen. Can be opposites. Narcissism can have inflated self-esteem and love of self.
Narcissism. The hallmark of a narcissist is an immense ego, grandiosity, and self-importance, as well as being entitled, and a tendency to use and objectify others as well as thinking of people in all-good or all-bad terms instead of shades of gray. The core of a narcissist is profound insecurity, and terrible self esteem.

Related Questions

Do all people with narcissistic personality disorder really have low self esteem?

Absolutely not. There are probably some types of narcissistic personality disorder that are based on trauma. In those cases I would agree that the core problem maybe low self-esteem secondary to trauma. However, for those people are born with a narcissistic temperament, they do not have trouble with low self-esteem, rather, they have a primary deficit in empathy.
Low esteen. Can be opposites. Narcissism can have inflated self-esteem and love of self.
Narcissism. The hallmark of a narcissist is an immense ego, grandiosity, and self-importance, as well as being entitled, and a tendency to use and objectify others as well as thinking of people in all-good or all-bad terms instead of shades of gray. The core of a narcissist is profound insecurity.

How do you tell the difference between complete low self-esteem and body dysmorphic disorder?

You need to have. A psychiatric evaluation. But bdd is an obsession with a minor or imaginary physical flaw. Someone with low self esteem is not generally concerned with one flaw.
Low self esteem. You could have low self esteem without body dysmorphic disorder or vice versa. In my experience both usually occur simultaneously. Best.