# Lactated Ringer’s versus normal saline

Andrew Bland, MD, FACP, FAAP · October 21, 2026

## Composition helps explain the acid–base effect

Typical LR contains sodium 130, chloride 109, potassium 4, calcium approximately 3 and lactate 28 mEq/L; formulation details vary. Normal saline contains sodium and chloride 154 mEq/L each, with no potassium, calcium or buffer. LR is commonly grouped with isotonic resuscitation crystalloids, although its measured osmolarity is slightly below plasma.

## Neither bag contains bicarbonate

Both LR and NS contain zero bicarbonate in the bag. LR provides lactate as a metabolizable bicarbonate precursor; NS has no buffer anion. Saline-associated hyperchloremic acidosis is sometimes described as dilutional or expansion acidosis, but chloride-rich composition—not volume expansion alone and not the acidity of the bag—is the central teaching point.

## Example bag pH is not the systemic acid–base effect

Example manufacturer labels list LR at pH 6.5 (range 6.0–7.5) and NS at pH 5.6 (4.5–7.0). Values vary by product and container. Bag pH is unitless and does not measure the delivered titratable acid load or predict the patient’s response; the chloride burden, metabolizable anions, dose and patient physiology matter far more.

## Why chloride rises while bicarbonate falls

A large chloride-rich saline load can raise chloride relative to sodium, lower the plasma strong-ion difference and produce a normal-anion-gap metabolic acidosis. This is not a claim that saline directly triggers bicarbonate loss at a particular tubular transporter. LR supplies less chloride and lactate that can be metabolized to a bicarbonate equivalent; the lactate anion is not an infusion of lactic acid.

## What the trials support—and what they do not

SMART found a small reduction in a composite of death, new dialysis or persistent renal dysfunction with balanced crystalloids. SALT-ED found a similar secondary kidney-composite signal, while its primary hospital-free-days outcome was unchanged. The large blinded PLUS and BaSICS trials did not establish a clear overall advantage in their primary mortality outcomes; PLUS also found similar kidney outcomes. These trials tested balanced-crystalloid strategies, sometimes LR or Plasma-Lyte and sometimes Plasma-Lyte alone. They do not prove that LR universally prevents AKI or that normal saline is a direct nephrotoxin.

## Choose the fluid for the clinical problem

A possible modest kidney benefit and less hyperchloremic acidosis support considering balanced crystalloids when appropriate. Chloride-depletion alkalosis may favor saline. Brain injury, severe sodium disorders, compatibility issues and specific electrolyte problems require a tailored plan. Fluid volume, indication and repeated reassessment remain central; these resuscitation studies should not be treated as proof of the best maintenance regimen.

## Sources

- [LR composition: prescribing information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=31d5a70d-d1fd-a5cd-e063-6394a90ac2f9)
- [0.9% saline composition: prescribing information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4d0bfd28-460a-48ba-bd17-cf75e56d62f4)
- [SMART randomized trial](https://www.nejm.org/doi/full/10.1056/NEJMoa1711584)
- [SALT-ED randomized trial](https://www.nejm.org/doi/full/10.1056/NEJMoa1711586)
- [PLUS randomized trial](https://www.nejm.org/doi/full/10.1056/NEJMoa2114464)
- [BaSICS randomized trial](https://jamanetwork.com/journals/jama/fullarticle/2783039)
- [LR label with pH range](https://dailymed.nlm.nih.gov/dailymed/downloadpdffile.cfm?setId=d6dd086f-f8d9-43ed-a215-2373dea73ec3)
- [Saline labels with pH range](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e44c41ae-c9c8-4dd8-ba6c-cebb585378aa)