I'm on 50mg sertraline and i read that it can cause low sodium, how likely is that and should i add more salt in my diet? if i eat late or not eat enough i feel weak and i'm worried it's hyponatremia?

Eating more salt will not help. If the cause is Sertraline you may want to discuss changing meds with Dr. Go to Drugs.com and look up all meds you are taking as many can cause low blood Na. Not likely at your age.

Low serum Na, hyponatremia, is a RARE side effect of SSRI & sertraline belongs to this group. You do not need to change your diet, only avoiding aggressively high fluid intake. Have a chemistry panel done one time 3 months after taking this medication then yearly is more than enough. By my experience, this complication is more common in elder women. Your symptoms are not symptoms of hyponatremia.