Research has long shown that an increase in sodium and oral fluid intake can increase blood and plasma volume, improve orthostatic tolerance, and decrease baroreceptor sensitivity in people with orthostatic hypotension and POTS.  

Vernino S, Bourne KM, Stiles LE, Grubb BP, Fedorowski A, Stewart JM, Arnold AC, Pace LA, Axelsson J, Boris JR, Moak JP, Goodman BP, Chémali KR, Chung TH, Goldstein DS, Diedrich A, Miglis MG, Cortez MM, Miller AJ, Freeman R, Biaggioni I, Rowe PC, Sheldon RS, Shibao CA, Systrom DM, Cook GA, Doherty TA, Abdallah HI, Darbari A, Raj SR. Postural orthostatic tachycardia syndrome (POTS): State of the science and clinical care from a 2019 National Institutes of Health Expert Consensus Meeting - Part 1. Auton Neurosci. 2021 Nov;235:102828. doi: 10.1016/j.autneu.2021.102828. Epub 2021 Jun 5. PMID: 34144933; PMCID: PMC8455420.   

Highlights: To expand blood volume, patients should have a minimum intake of 2 to 3 L of water per day along with increased sodium intake. Most clinicians recommend oral sodium intake to avoid potential complications of intravenous access. Sodium intake can be increased to 3 to 10 g daily using ordinary table salt (1 tsp. is approximately 2.3 g sodium), salt tablets or electrolyte solutions.   

Garland EM, Gamboa A, Nwazue VC, Celedonio JE, Paranjape SY, Black BK, Okamoto LE, Shibao CA, Biaggioni I, Robertson D, Diedrich A, Dupont WD, Raj SR. Effect of High Dietary Sodium Intake in Patients With Postural Tachycardia Syndrome. J Am Coll Cardiol. 2021 May 4;77(17):2174-2184. doi: 10.1016/j.jacc.2021.03.005. PMID: 33926653; PMCID: PMC8103825.   

Highlights: Patients received 6 days of LS (10 mEq sodium/day) or HS (300 mEq sodium/day) diet. In POTS patients, high dietary sodium intake compared with low dietary sodium intake increases plasma volume, lowers standing plasma norepinephrine, and decreases changes in heart rate.    

El-Sayed H, Hainsworth R. Salt supplement increases plasma volume and orthostatic tolerance in patients with unexplained syncope. Heart. 1996;75(2):134-140. doi:10.1136/hrt.75.2.134   

Highlights: Participants took capsules containing 10 mmol sodium chloride or placebo (12 per day). In the open study, they took slow sodium (Ciba) (10 mmol, 12 per day). In patients with unexplained syncope who had a relatively low salt intake administration of salt increased plasma volume and orthostatic tolerance, and in the absence of contraindications, salt is suggested as a first line of treatment.