The vast majority of people who are online use social media, often for hours a day. For most, there is no problem. For others, it crosses the line into addiction. When does normal connectivity become a problem?
One way to measure is the Bergen Social Media Addiction Scale (originally designed for Facebook but since generalized for all social media). It's a short survey used in psychological research that has been widely accepted by the psychology community. It's quick and something you can take yourself.
Here are six statements to consider. For each, answer: (1) very rarely, (2) rarely, (3) sometimes, (4) often, or (5) very often.
If you scored a 4 or 5 ("often" or "very often") on at least 4 of those statements, it could be an indicator of social media addiction.
Interesting side note: Scoring higher on this scale was correlated with later bedtimes and wake-up times. Whether that means night owls are more likely to be addicted or addiction keeps people up late is something for future research...
Andreassen, C. S., Torsheim, T., Brunborg, G. S., & Pallesen, S. (2012). Development of a Facebook addiction scale. Psychological reports, 110(2), 501-517.