What are the side effects of injectable PrEP?

Injectable PrEP is well tolerated. Here's what to realistically expect.

The vast majority of people take cabotegravir injections without major difficulty. That said, side effects do occur, and some may be more intense or last longer than expected.

Injection site reactions: the most common effect

This is the expected effect of any intramuscular injection. It's normal to experience some of the following in the days after your shot:

Pain or tenderness to the touch
Redness or mild swelling
Induration (a small lump or hardened area under the skin)

These reactions typically decrease after the first few injections as your body adjusts. A cold compress and over-the-counter analgesics can help. Individualized advice on managing discomfort is available from our team if needed.

Flu-like symptoms: common especially at first

After the first injections (particularly the 1st and 2nd), around 5% of people may experience:

Fatigue, muscle aches, headaches
Mild fever or chills

These symptoms generally resolve within 24 to 48 hours, sometimes over a few days. They tend to be more pronounced following the first 2 injections and ease with subsequent doses.

Acetaminophen (Tylenol®) is generally enough to manage them. If you're unsure what to take, or if your symptoms seem unusual or persist, call your pharmacy. We can provide individualized support.

What if side effects are hard to tolerate?

It's uncommon, but it happens. Clinical data — and our on-the-ground experience — suggest that roughly 3 to 5% of people on injectable PrEP eventually consider switching treatments, including those for whom side effects are too uncomfortable. If that's your situation, options exist. We can work through them together and find what works best for you.

Other possible effects

Like any medication, cabotegravir may cause other less common effects. If you notice something unusual after your injection, don't try to interpret it on your own and contact us. We're better positioned to help you assess whether it's related to your treatment.