The Deal with PrEP Labs

Know exactly what is tested for and why when taking PrEP.

July 12, 2021

PrEP stands for Pre (before) Exposure (coming into contact with something) Prophylaxis (prevention of disease). PrEP describes a way of taking a once-daily anti-HIV medication that reduces the risk of acquiring HIV through sex by ~99% and through IV drug use by ~74% when taken as directed. Truvada and Descovy are the brand names most associated with PrEP, but all FDA-approved pills for PrEP contain the same backbone of medicines: tenofovir and emtricitabine. When someone says they are taking PrEP, that usually means they are taking an approved medication, getting regular lab tests to check in on their health, and are in contact with a healthcare provider about their health concerns.

Why do we need labs?

PrEP requires monitoring of HIV status, kidney function, and Hepatitis B status in order to start and continue the medication. Because of how PrEP interacts with the body and/or other medications, there are a few things we need to keep track of:

Most importantly, we test for HIV to start or restart PrEP & then every 3 months.

PrEP is designed to help people remain HIV-negative, so it is important to know your HIV status as you start or continue the medication. As PrEP isn’t a complete regimen to manage HIV, there is a risk of drug resistance to HIV-medication if PrEP continues to be taken despite HIV-infection. Resistance to PrEP means that it is no longer as effective in preventing the transmission of HIV. This is more likely to occur while taking PrEP only some of the time. Or to put it another way, if you take PrEP only a few times a week, and you get HIV but continue taking PrEP, the virus  can become resistant to the medication. This drug resistance is more likely to happen during periods of undiagnosed acute HIV infection.

There are two different types of HIV tests:

  • 3rd generation HIV test
  • This test checks for the antibody made by the immune system to fight off HIV
  • It takes time for the body to produce the antibody, which is why this test can stay negative for up to 3 months after an HIV infection happens
  • Saliva tests and certain finger prick tests are 3rd generation tests
  • FOLX offers the 4th generation HIV test
  • This test checks for both the antibody and the antigen, a structure on the HIV virus 
  • This test detects HIV infection much earlier than the 3rd generation test
  • If this test comes back positive and there’s enough blood left on the sample, a second test is done to confirm HIV status

Labs are required to report positive HIV test results to your local Department of Health. They will contact you to see if you have been connected with HIV care and will ask about recent sexual partners to make sure they also have access to testing and care. You decide what and how much information you want to give them. This type of reporting is actually quite common, and is also required of other infections such as: chickenpox, gonorrhea, lyme disease, tetanus, and several others.

We also closely monitor kidney function (creatinine test) to start or restart PrEP, 3 months after starting, and then every 6 months.

Medications containing tenofovir -- like the medications approved for PrEP (TDF/FTC) -- are removed from the body by the kidneys. It is normal to see small decreases in kidney function. In the small number of patients (~1 in 200) who do see a significant decrease in kidney function, these changes usually reverse themselves after stopping the medication.  However, for folx who already have kidney problems, the medication worsens kidney failure. Kidney failure can also happen for those who have other health conditions or take medications that affect the kidneys. People interested in PrEP should have a baseline and periodic tests of kidney function.

And we check for Hepatitis B to start or restart PrEP.

While PrEP can be used to treat hepatitis B infection, stopping PrEP with an active hepatitis B infection can in very rare cases lead to liver inflammation or liver failure. Our test looks for a current hepatitis B infection. There are other tests that can tell if you’re immune to hepatitis B. If you are immune to hepatitis B, then this means that you can’t be infected with hepatitis B and you don’t need any more testing done.

What other labs/tests do we recommend?

At FOLX, we want to only run labs that are necessary for the care we are providing so we can keep costs low for members. PrEP comprises one part of our members' sexual health toolkit. If relevant to you, other tests to consider are quarterly screening tests for chlamydia, gonorrhea, and syphilis, and annual screening tests for hepatitis C.

FOLX pairs lab results with our members’ lived experiences to come to final medical decisions.

At FOLX, we do not base medical decisions solely on labs. It is much more important to hear from our members about how they are feeling. We will communicate with our members about any lab results, and if there are any concerns from a medical perspective. We want to hear from the members themselves about what feels right in their body and how they want to move forward before finalizing any changes.

FOLX wants to make getting labs done easy.

Presently, FOLX offers three different options to keep on top of PrEP labs:

  • Go to a Quest Diagnostics: FOLX will order labs to a member’s nearest Quest Diagnostics PSC (Patient Service Center) to go and get blood drawn in person. Quest will send lab results directly to FOLX.
  • At-home lab kits: FOLX will ship a finger-prick kit directly, and members are required to deposit a finger-prick blood sample and then send the kit back to our partner lab by mail.
  • Get & send your own labs: If it’s easier to have insurance pay for labs, or member has an existing clinic that will order labs for them, then labs just need to be uploaded and sent to FOLX.

So, that’s it for PrEP labs. FOLX is currently able to prescribe PrEP to be shipped directly to members, and the process begins here. For existing FOLX members, don't hesitate to schedule time with a clinician or to reach out to your clinician on your portal. And for those who want to know more, read up on all things about sexual health here, and feel free to reach out to us at

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