Remember that the kidneys excrete salt at a higher rate when we don’t eat carbohydrate, so we have to work a bit harder to keep our salt intake up. Not only that, but recent research at McMaster University and elsewhere has shown that we are healthiest when getting quite a bit more salt than current guidelines advise. About 5 grams a day (probably somewhat more for people in ketosis) of sodium translates to about 2.5 tsp of salt a day, but remember that this includes the salt in your food.
The studies show that the risk curve is much steeper, the more one reduces salt, than when one increases salt, so it is a bit safer to get too much than to get too little. For people who have high blood pressure, however, the risk from too much salt is higher, and rises faster as intake increases.