Why do my hands feel so cold indoors. i am 28. is this worth mentioning to my doctor, is it serious?

Yes, Please let the Doctor know and he/she may choose to check it out. While Symptoms known as Raynaud's Phenomenon tend to occur more frequently in Females and more outdoors than indoors - there is not an immutable law.- Besides there may be several other explanations for what one is feeling.

If this is a long-standing tendency it's probably an intolerance to colder temperatures seen in many people including slender people. The body is shunting warmth from the peripheral areas of the body ( hands,feet,nose) & sending more circulation to the interior. Anxiety causes cold but sweaty hands. If it's a new development, we check for underactive thyroid, anemia,etc. so see your physician