Skip to main content

Phenol Red Thread Test

Zone-Quick

Calculate dosage
Sourced from primary literature. Awaiting credentialed clinical reviewer — our editorial process.

Drug Class

Diagnostic

Routes

TOPICAL (ophthalmic)

Indications

Tear production measurement

Mechanism of Action

pH-sensitive dye thread placed in lower conjunctival fornix. Tears change thread color from yellow to red, measuring tear production in 15 seconds.

Side effects & warnings

Less invasive than Schirmer tear test. Good for exotic species and cats. Normal values differ by species. Not a therapeutic agent.

Species with Phenol Red Thread Test dosing data (2 dose rules)

Cat (Domestic)Dog (Domestic)

Evidence levels across 2 dose rules

Moderate×2

Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.

Backed by a published primary source

  • · Plumb's Veterinary Drug Handbook, 9th Ed

Sample dosing (2 of 2 cited rules)

Free-tier preview — dog and cat dosing. Pro and Student unlock all 2 species including reptiles, birds, pocket pets, livestock, and equine.

SpeciesRouteDoseFrequencyEvidenceSource
Dog (Domestic)TOPICAL (ophthalmic)0 1 thread per eyePRN (diagnostic)ModeratePlumb's Veterinary Drug Handbook, 9th Ed
Cat (Domestic)TOPICAL (ophthalmic)0 1 thread per eyePRN (diagnostic)ModeratePlumb's Veterinary Drug Handbook, 9th Ed

Upgrade for Full Details

Upgrade to Pro or Student to access full drug details including mechanism of action, warnings, dose ranges, and frequency.

View Plans

More Diagnostic drugs

Calculate Dosage for Phenol Red Thread Test