@benrickert said in Swollen legs from sitting:

Can they be two different things?

Yes, but there is a tight interconnection.
And if I were you, I'll get informed on how to balance a higher level with sodium.
Don't believe what you're going to read about excess salt.
Here is some useful info, on my forum.

Understanding how sodium works – Importance of sodium in cellular exchanges
https://mirzoune-ciboulette.forumactif.org/t1362-comprendre-le-fonctionnement-du-sodium?highlight=sodium (In French; translator needed)
Extract:
“Salt can help lower inflammation, increase womb healing, metabolize better and therefore fuel well, help you sleep, improve muscle function, and have a positive effect on your blood pressure. »
Kate DEERING.

Sodium and Potassium Balance – Compensation by the body (In French)
https://mirzoune-ciboulette.forumactif.org/t1068-equilibre-sodium-et-potassium-compensation-par-lorganisme?highlight=sodium
Key ideas
• The pH of the cellular environment is decisive for proper enzymatic functioning. The body will therefore regulate this pH carefully. If it is overwhelmed, a host of pathologies could make their bed, sometimes in a delayed manner...
• The body will seek to compensate with different buffer systems.
• To correct the terrain, potassium is the key nutrient. But every time you ingest excess salt, by considering your potassium reserves, you will disrupt this balance.
• The metabolism will correct the situation with an H+ ion to maintain the correct gradient: An H+ ion will replace a K+ ion. In doing so, the pH is modified and moves towards acidosis.
• The movements of water across cell membranes follow the movements of sodium, which themselves are only possible if a sodium ion is exchanged for a potassium ion (K+) or a hydrogen ion (H+) for reasons of electro-neutrality. Thus, the distribution of water in the body is a function of these ion exchanges.

Salt – Against the grain! What to do in case of water retention? (In French)
https://mirzoune-ciboulette.forumactif.org/t599-sel-a-contre-courant-que-faire-en-cas-de-retention-deau?highlight=sodium
Quote:

“One of the things that happen when there isn’t enough sodium in the diet is that more aldosterone is synthesized.

Aldosterone causes less sodium to be lost in the urine and sweat, but it achieves that at the expense of the increased loss of potassium, magnesium, and probably calcium. The loss of potassium leads to vasoconstriction, which contributes to heart and kidney failure and high blood pressure. The loss of magnesium contributes to vasoconstriction, inflammation, and bone loss. Magnesium deficiency is extremely common, but a little extra salt in the diet makes it easier to retain the magnesium in our foods."
By Ray Peat, PhD. Salt, energy, metabolic rate, and longevity 2007.