What Are the Side Effects of Cholesterol Shots Like Repatha or Praluent?

What are the most common side effects of cholesterol shots like Repatha or Praluent?

The most common reported effects include reactions where the injection goes in, cold-like or flu-like symptoms, muscle aches, back pain, and diarrhea. The exact pattern and frequency differ between medicines and studies.

The FDA’s 2025 Repatha prescribing information reports that, in a 52-week controlled trial, nasopharyngitis occurred in 10.5% of Repatha patients versus 9.6% on placebo. Upper respiratory infection occurred in 9.3% versus 6.3%, back pain in 6.2% versus 5.6%, myalgia in 4.0% versus 3.0%, and diarrhea in 3.0% versus 2.6%. Those figures describe events reported during the trial; a small difference between groups does not prove the cause of an individual person’s symptom.

In controlled adult trials in the FDA’s 2025 Praluent prescribing information, injection-site reactions occurred in 7% of treated patients versus 5% on placebo. Influenza occurred in 6% versus 5%, diarrhea in 5% versus 4%, myalgia in 4% versus 3%, and muscle spasms in 3% versus 2%. These are study findings, not a prediction of what any one patient will experience.

Patient reviews can add context about what people notice, but they cannot show how common a symptom is or prove the injection caused it. A symptom can begin after a dose and still have another cause. For a broader view than any one review, the systematic review in Heart examined 32 randomized trials involving 65,861 participants; it found that PCSK9 inhibitors probably do not increase myalgia or muscular pain leading to discontinuation.

Can a cholesterol shot cause muscle or joint pain, fatigue, or diarrhea?

Muscle aches and diarrhea are listed in prescribing information for both medicines, but trial rates were only modestly higher than placebo in the cited results. MedlinePlus also lists muscle or back pain, flu-like symptoms, dizziness, headache, and stomach pain as possible effects of evolocumab.

Fatigue and joint pain are concerns some patients may mention in reviews, but the supplied trial figures do not establish their frequency for either medicine. The sources here do not provide a reliable percentage for fatigue or joint pain, so those symptoms should not be presented as common based on anecdotes alone.

Look at the pattern, not just the timing. Note the day symptoms start, their severity, how long they last, and whether they return after an injection. Include new medicines or supplements in that record. This gives the prescriber useful detail to weigh against other possible causes and the benefits of ongoing cholesterol treatment.

How long do side effects after a Repatha or Praluent injection last?

There is no standard duration for typical side effects in the supplied sources. MedlinePlus advises contacting a clinician if evolocumab side effects are severe or do not go away, but it does not give a usual number of hours or days for them to resolve.

Track when each symptom begins and ends rather than assuming all effects follow one timeline. A brief, mild symptom and one that persists, worsens, or returns are different clinical details. Tell the prescriber which injection you use and when the symptoms occur in relation to it.

The Heart systematic review assessed trials with a median follow-up of 40 weeks, ranging from 24 to 146 weeks, but that study duration does not describe how long an individual reaction lasts. Duration for a particular person depends on the symptom and its cause; the available sources do not settle that question for every effect.

Is redness, swelling, bruising, or itching at the injection site normal?

Redness, pain, bruising, itching, swelling, or tenderness can occur at the injection site, and the prescribing information reports these reactions in clinical studies. They are usually not, by themselves, proof of a serious allergy.

The FDA’s 2025 Repatha label reports injection-site reactions in 5.7% of patients in one 52-week trial versus 5.0% on placebo; pooled controlled trials reported 3.2% versus 3.0%. Only 0.1% discontinued Repatha in the pooled trials because of these reactions. In the FDA’s 2025 Praluent label, pooled placebo-controlled studies reported local reactions in 7.2% versus 5.1%; discontinuation for these reactions was uncommon, at 0.2% versus 0.4%.

For Praluent, the FDA label recommends choosing skin that is not tender, bruised, red, or hardened and rotating injection sites. Contact the prescriber if a local reaction is severe, persistent, or worsening. Swelling of the face or throat, breathing difficulty, or other signs of a serious allergic reaction are a different matter and need immediate medical attention.