Is bacteriostatic water the same as sterile water?

No. Both are sterile at manufacture, but bacteriostatic water adds a benzyl alcohol preservative and comes in a multiple-dose vial; sterile water has no preservative and comes only in single-dose containers.

What's the difference between bacteriostatic water and sterile water for injection?

Bacteriostatic water for injection, USP contains 0.9% or 1.1% benzyl alcohol as a preservative for multi-dose use. Sterile water for injection, USP contains no preservative and is single-dose only.

Can I use sterile water instead of bacteriostatic water for peptides?

Check the product label. Some lyophilized peptide labels, like EGRIFTA SV, specify sterile water for single-dose, immediate-use reconstitution rather than bacteriostatic water.

Does the preservative in bacteriostatic water affect peptide stability?

A 2017 Journal of Pharmaceutical Sciences study by Arora et al. found common preservatives, including benzyl alcohol, lowered a protein's conformational stability and raised aggregation versus no preservative.

How long can an opened bacteriostatic water vial be used?

FDA guidance on multi-dose vials generally recommends discarding an opened vial within 28 days of first use, since contamination risk rises after that window.

Why do reconstitution instructions say not to shake the vial?

Labels for cetrorelix acetate, glucagon, and infliximab (Remicade) all instruct gentle swirling; the cetrorelix label warns that shaking creates bubbles, and the Remicade label says not to shake.

What preservative is in bacteriostatic water and how much?

Benzyl alcohol (C7H8O, molecular weight 108.14 per PubChem), added at 0.9% (9 mg/mL) or 1.1% (11 mg/mL), per the Hospira FDA label.

PreppinPeppers › Facts › Lab article

Bacteriostatic Water vs Sterile Water for Peptides Compared

Machine-readable facts for this Lab article. The full page is https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials.

TL;DR

Bacteriostatic water contains a 0.9%-1.1% benzyl alcohol preservative for repeated draws from one multi-dose vial, while sterile water has no preservative

Facts Index

Fact ID	Category	Entity	Attribute	Value	Source
which-diluent-is-actually-right-for-your-peptide-vials:title	identity	Bacteriostatic Water vs Sterile Water for Peptides Compared	title	Bacteriostatic Water vs Sterile Water for Peptides Compared	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:published	identity	Bacteriostatic Water vs Sterile Water for Peptides Compared	published	2026-10-03	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:last-reviewed	identity	Bacteriostatic Water vs Sterile Water for Peptides Compared	last reviewed	2026-10-03	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:author	identity	Bacteriostatic Water vs Sterile Water for Peptides Compared	author	Preppin' Peppers Editorial Team	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:topics	identity	Bacteriostatic Water vs Sterile Water for Peptides Compared	topics	Education, guide, peptide education	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:summary	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	summary	Bacteriostatic water contains a 0.9%-1.1% benzyl alcohol preservative for repeated draws from one multi-dose vial, while sterile water has no preservative	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:section-1	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	section	What's the difference between bacteriostatic water and sterile water for peptide reconstitution?	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:section-2	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	section	Why does the preservative in bacteriostatic water matter for your peptides?	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:section-3	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	section	When do peptide product labels call for sterile water instead?	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:section-4	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	section	What goes wrong when a multi-dose vial gets reused too many times?	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:section-5	content	Bacteriostatic Water vs Sterile Water for Peptides Compared	section	What do researchers get wrong about bacteriostatic water vs sterile water?	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:product-gansulin-metal-peptide-pen	products	Bacteriostatic Water vs Sterile Water for Peptides Compared	references product	Gansulin Pen · Reusable Click-Dial, 3 ml (1-60 Units)	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:product-gansulin-3ml-cartridge	products	Bacteriostatic Water vs Sterile Water for Peptides Compared	references product	Gansulin-Compatible 3 ml Glass Cartridge for Pens (10-Pack)	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-pubmed-ncbi-nlm-nih-gov	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	Meyer et al., J Pharm Sci 2007: Antimicrobial preservative use in parenteral products: past and present - pubmed.ncbi.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-pubmed-ncbi-nlm-nih-gov-2	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	Mattner and Gastmeier, Am J Infect Control 2004: Bacterial contamination of multiple-dose vials: a prevalence study - pubmed.ncbi.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-pubmed-ncbi-nlm-nih-gov-3	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	Arora et al., J Pharm Sci 2017: Correlating the Effects of Antimicrobial Preservatives on Conformational Stability, Aggregation Propensity, and Backbone Flexibility of an IgG1 mAb - pubmed.ncbi.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-pubchem-ncbi-nlm-nih-gov	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	NCBI PubChem CID 244: Benzyl Alcohol (C7H8O) - pubchem.ncbi.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	Bacteriostatic Water for Injection, USP: FDA label on DailyMed, U.S. National Library of Medicine (0.9% benzyl alcohol) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov-2	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	FDA label (DailyMed): Sterile Water for Injection, USP (Cardinal Health) - prescribing label (retrieved 2026-10-03) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov-3	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	FDA label (DailyMed): EGRIFTA SV (tesamorelin for injection) 2 mg vial, Theratechnologies - preparation, description and storage (retrieved 2026-10-03) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov-4	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	FDA label (DailyMed): Cetrorelix Acetate for Injection 0.25 mg (lyophilized peptide), Meitheal - patient instructions and storage (retrieved 2026-10-03) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov-5	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	FDA label (DailyMed): Glucagon for Injection kit (lyophilized peptide hormone), Amphastar - preparation instructions (retrieved 2026-10-03) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-dailymed-nlm-nih-gov-6	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	FDA label (DailyMed): REMICADE (infliximab) lyophilized powder for injection, Janssen - reconstitution instructions (retrieved 2026-10-03) - dailymed.nlm.nih.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)
which-diluent-is-actually-right-for-your-peptide-vials:source-www-fda-gov	source	Bacteriostatic Water vs Sterile Water for Peptides Compared	cites	U.S. FDA drug alert: concerns with unapproved GLP-1 drugs (content current as of 10/01/2026) (retrieved 2026-10-03) - www.fda.gov	Lab article (https://www.preppinpeppers.com/blogs/the-lab/which-diluent-is-actually-right-for-your-peptide-vials) (evidence)

FAQ

Is bacteriostatic water the same as sterile water?: No. Both are sterile at manufacture, but bacteriostatic water adds a benzyl alcohol preservative and comes in a multiple-dose vial; sterile water has no preservative and comes only in single-dose containers.
What's the difference between bacteriostatic water and sterile water for injection?: Bacteriostatic water for injection, USP contains 0.9% or 1.1% benzyl alcohol as a preservative for multi-dose use. Sterile water for injection, USP contains no preservative and is single-dose only.
Can I use sterile water instead of bacteriostatic water for peptides?: Check the product label. Some lyophilized peptide labels, like EGRIFTA SV, specify sterile water for single-dose, immediate-use reconstitution rather than bacteriostatic water.
Does the preservative in bacteriostatic water affect peptide stability?: A 2017 Journal of Pharmaceutical Sciences study by Arora et al. found common preservatives, including benzyl alcohol, lowered a protein's conformational stability and raised aggregation versus no preservative.
How long can an opened bacteriostatic water vial be used?: FDA guidance on multi-dose vials generally recommends discarding an opened vial within 28 days of first use, since contamination risk rises after that window.
Why do reconstitution instructions say not to shake the vial?: Labels for cetrorelix acetate, glucagon, and infliximab (Remicade) all instruct gentle swirling; the cetrorelix label warns that shaking creates bubbles, and the Remicade label says not to shake.
What preservative is in bacteriostatic water and how much?: Benzyl alcohol (C7H8O, molecular weight 108.14 per PubChem), added at 0.9% (9 mg/mL) or 1.1% (11 mg/mL), per the Hospira FDA label.