Oral vs. injectable PrEP: a lab-monitoring checklist for telehealth and clinic programs
Every PrEP prescription rests on lab work. CDC's Clinical Guidance for PrEP is clear that clinicians must confirm a patient doesn't have HIV before starting PrEP and keep confirming it for as long as the patient stays on it.
What changes from one PrEP option to the next is the rhythm. Daily oral pills, injectable cabotegravir (CAB) every 2 months and injectable lenacapavir (LEN) every 6 months each come with their own testing calendar, and many programs now offer more than one. This checklist compares the lab requirements side by side and turns them into questions to settle with your lab partner.
If you want the full visit-by-visit schedule and a look at where remote programs lose patients, start with our earlier guide to PrEP lab monitoring for telehealth programs. This post focuses on the comparison and what it means for program operations.
This is an operational summary for program leaders, not medical advice. Prescribing clinicians should follow CDC guidance and their own protocols, and decide which tests each patient needs.
The baseline checklist
Before anyone starts PrEP, CDC recommends:
HIV testing for everyone, using an HIV antigen/antibody (Ag/Ab) test, plus an HIV-1 RNA test when recent PrEP or PEP use or recent exposure calls for it
Chlamydia, gonorrhea and syphilis screening for all sexually active adults starting oral or injectable PrEP
Serum creatinine to estimate creatinine clearance (eCrCl) for oral PrEP with F/TDF or F/TAF
Hepatitis B screening for everyone considered for oral PrEP
A lipid profile for patients starting F/TAF
Kidney testing isn't needed for patients on injectable CAB. For LEN, CDC's 2025 clinical recommendation calls for a negative blood-based HIV Ag/Ab result within 7 days before the first injection, a confirmatory HIV-1 RNA test if available (the RNA result shouldn't delay the first injection), STI screening, and a check of hepatitis B status for patients switching from tenofovir-based PrEP.
Ongoing monitoring, side by side
Daily oral PrEP (F/TDF or F/TAF)
At least every 3 months: HIV Ag/Ab and HIV-1 RNA, with refills written for no more than 90 days, until the next HIV test
At least every 6 months: syphilis and gonorrhea screening for all sexually active PrEP users, plus chlamydia for gay and bisexual men; eCrCl for patients 50 or older or who started with an eCrCl under 90 mL/min
At least every 12 months: eCrCl for everyone on oral PrEP, lipids for patients on F/TAF, and chlamydia screening for heterosexually active patients
Injectable cabotegravir, every 2 months
Month 1, then at least every 2 months from month 3: HIV Ag/Ab and HIV-1 RNA at each injection visit
At least every 4 months from month 3: bacterial STI screening for gay and bisexual men (oral, rectal, urine and blood)
At least every 6 months from month 7: bacterial STI screening for heterosexually active patients
After stopping: quarterly HIV Ag/Ab and HIV-1 RNA for 12 months, because CAB levels fade slowly during what CDC calls the "tail period"
Injectable lenacapavir, every 6 months
Before each injection: a negative HIV Ag/Ab result, ideally lab-based on the day of the injection or within the previous 7 days. If a rapid test is used before an injection, CDC says to also send a confirmatory lab-based Ag/Ab test
At each visit: STI screening based on risk, which CDC notes may need to happen more often than the injection visits themselves
Sources: CDC Clinical Guidance for PrEP and the CDC lenacapavir recommendation.
What the comparison means for operations
Laid side by side, the three calendars put very different demands on a program and its lab.
HIV testing frequency varies widely. By CDC's minimums, an oral PrEP patient needs an HIV Ag/Ab and RNA result at least four times a year, a CAB patient about six times a year, and a LEN patient twice a year. A program offering all three is effectively running three order sets.
The result has to arrive before the medication. For oral PrEP, a late result holds up a refill. For injectables, the HIV test is tied to the injection visit itself, so collection timing and result delivery need to line up with the appointment calendar, not just the end of a quarter.
STI screening doesn't follow the injection clock. A LEN patient may need STI screening more often than every 6 months, and CAB schedules differ for gay and bisexual men and for heterosexually active patients. Treat STI orders as their own track.
Specimen sites matter. CDC calls for oral, rectal and urine sites as indicated, plus blood for syphilis. For gay and bisexual men and other LGBTQ+ patients with those exposures, urine-only screening can miss infections.
People who stop still need testing. CAB's tail period means a year of quarterly HIV testing after the last injection. LEN levels also decline slowly after it's stopped, so clinicians need a plan for follow-up and other prevention options.
Telehealth doesn't remove the lab visit. CDC says lab-only visits for HIV and other indicated tests are "strongly preferred" for telehealth PrEP, and advises against oral-swab HIV self-tests except when no lab or clinic visit is possible.
Questions to ask your PrEP lab partner
Can you run every test on all three calendars under one account? That includes HIV Ag/Ab, HIV-1 RNA, syphilis, chlamydia and gonorrhea at each indicated site, creatinine, hepatitis B and lipids.
Can order sets match each regimen? Oral, CAB and LEN patients need different panels at different intervals, and clinicians shouldn't have to rebuild them by hand.
How do you set and report turnaround targets? Ask specifically about HIV-1 RNA, since injectable visits depend on it, and how you'll be told if a result is delayed.
What happens with a reactive or unclear HIV result? Who gets called, how fast, and how does a new specimen get collected? CDC recommends drawing a new blood specimen for repeat testing 5 to 7 days after an ambiguous result.
Can results flow into our platform? An API or EHR feed beats a PDF someone has to download before a refill or injection.
Which states are you licensed in? Some states have their own lab licensing rules, so match the lab's licenses to the states you serve.
Frequently asked questions
Do injectable PrEP patients need kidney testing?
CDC says kidney assessments aren't necessary for patients taking injectable CAB, and kidney monitoring isn't part of CDC's LEN recommendation. Patients on oral PrEP need eCrCl at baseline and at least once a year, or every 6 months in some cases.
Why is HIV-1 RNA tested along with the antigen/antibody test?
Very early HIV infection can be missed by tests that rely on antibodies, and CDC notes that some tests may not detect recent infection in people taking PrEP medications. That's why CDC pairs Ag/Ab testing with HIV-1 RNA for oral PrEP and CAB, and recommends a confirmatory RNA test, if available, when a patient starts LEN.
Can telehealth patients use at-home HIV self-tests for PrEP monitoring?
CDC generally doesn't recommend oral-swab HIV self-tests for PrEP patients because they may not detect recent infection. Lab-based testing on a blood specimen is the standard.
Where IHDLab fits
IHDLab is a CLIA-certified laboratory (CLIA 05D2040304) in Irvine, California, licensed in California, New York and Maryland. We work business to business with telehealth companies, clinics and providers and community programs, running HIV Ag/Ab, HIV-1 RNA, syphilis, 1-site and 3-site chlamydia and gonorrhea, creatinine, hepatitis B and C, and lipid testing ordered by their licensed clinicians. IHDLab doesn't prescribe PrEP.
If you're planning panels for more than one PrEP option, our PrEP and STI lab testing overview is a good place to compare notes.
