Ovidrel: Side Effects, Timing, and What to Expect

You have an Ovidrel pen sitting in your fridge, and at some point in the next 24 to 48 hours, you will be the one giving the injection. This post is a practical walk-through of what Ovidrel is, how to inject it, what side effects are normal in the first 48 hours, and when something is unusual enough to call the clinic.

The good news is that Ovidrel is one of the more straightforward injections you will encounter in fertility treatment. The dose is fixed, the pen is prefilled, the needle is short, and most people feel no more than mild bloating in the day after the shot. The aim here is to give you enough specifics that the injection itself stops being a source of anxiety, and you can spend that mental energy elsewhere.

What Ovidrel actually is

Ovidrel is the brand name for choriogonadotropin alfa, a recombinant form of human chorionic gonadotropin (hCG).¹ Recombinant means the drug is produced in genetically engineered cell cultures, not extracted from the urine of pregnant women, which was the manufacturing route for the older formulations like Novarel and Pregnyl. The biological molecule that ends up in the syringe is functionally identical to natural hCG.

The pen contains a single 250 microgram dose, which is biologically equivalent to roughly 5,000 to 10,000 international units (IU) of urinary hCG.² That dose is the standard for ovulation induction, intrauterine insemination (IUI), and many in-vitro fertilisation (IVF) trigger protocols. The drug is supplied as a clear, colourless solution in a prefilled subcutaneous syringe with the needle already attached.

When patients ask whether Ovidrel is the same as Pregnyl or Novarel, my answer is that they are clinically equivalent for the purpose of triggering ovulation. Large head-to-head trials have not found meaningful differences in pregnancy outcomes between recombinant and urinary hCG.² The differences between them are practical: Ovidrel is prefilled and ready to inject, while urinary hCG comes as a powder you have to mix with a diluent before drawing into a syringe. Ovidrel is also typically more expensive in the US market, though insurance coverage varies widely.

How to inject Ovidrel

The injection is subcutaneous, which means it goes into the layer of fat just under the skin, not into muscle. The two recommended sites are the lower abdomen, roughly 2 inches away from the navel, or the front of the thigh. Both sites work equally well. Many patients prefer the abdomen because it is easier to pinch a fold of skin there.

Here is the practical sequence I walk patients through.

1. Take the pen out of the fridge roughly 30 minutes before use, so the medication is closer to body temperature when injected. Cold liquid stings more.
2. Wash your hands with soap and water. Wipe the injection site with an alcohol swab and let it air dry.
3. Remove the pen cap and check the liquid. It should be clear and colourless. Do not use the pen if the liquid is cloudy or has particles in it.
4. Pinch a fold of skin at the chosen site between your thumb and index finger.
5. Insert the needle at 90 degrees to the skin, in a quick smooth motion.
6. Push the plunger slowly until all the liquid is delivered.
7. Hold the needle in place for 5 seconds, then withdraw it at the same angle.
8. Press a clean cotton ball or gauze to the site for a few seconds; do not rub.
9. Discard the pen immediately into a sharps container, or, if you do not have one, a sturdy capped plastic bottle (laundry detergent or large soft-drink bottles work).

Most clinics will show the injection in advance, either in person or via a video your nurse sends through. If you have not had that demonstration and the appointment is tomorrow, call the clinic tonight. It is a 90-second piece of teaching and they will walk you through it.

A partner can give the injection if you prefer. There is nothing about the injection that requires you to do it yourself. What matters is that the injection goes in at the time your RE prescribed.

Why timing matters

Trigger time is one of the few moments in a medicated cycle where 30 minutes genuinely matters. Ovulation occurs approximately 36 to 40 hours after the injection,³ and if an IUI is scheduled at the clinic the following morning, that slot has been chosen to fall within that window. Taking the shot an hour late shifts ovulation by an hour. Taking it the wrong night entirely is a cycle-disrupting mistake.

For this reason, set at least two phone alarms for the trigger time. Some clinics schedule trigger for late evening, usually somewhere between 9pm and midnight, so that the IUI the following morning at 9am lands in the optimal pre-ovulation window. Some clinics use afternoon triggers if their IUI slots are in the afternoon. Whatever time your nurse gives you, follow it to the hour.

If you take the shot more than an hour late, call the clinic. Sometimes the IUI can be moved; sometimes the cycle is salvageable as is. Do not improvise.

Side effects to expect

The medication's job is to start a cascade that ends in ovulation, so most of what you feel in the first 48 hours is your ovary responding to the signal rather than the drug itself.

The most common side effect is mild abdominal bloating, usually starting 12 to 24 hours after the shot and resolving over the next 2 to 3 days. The bloating is from the dominant follicle finishing its growth and from mild peritoneal fluid as ovulation approaches. It feels something like premenstrual abdominal heaviness, occasionally more pronounced.

Some people also notice mild pelvic fullness or a one-sided pulling sensation around the time the egg is being released. This is similar to the mittelschmerz some people feel naturally at ovulation, and it tends to localise to the side where the dominant follicle was.

Breast tenderness can appear in the days after the shot. This is mostly from rising progesterone in the early luteal phase, not the trigger itself, and is the same tenderness many people get in any natural luteal phase.

A few people report mild fatigue, headache, or low mood in the first day or two. These are not the most common reactions, but they are recognised and they pass.

Injection-site reactions are uncommon. A small patch of redness around the needle entry, fading within hours, is normal. Significant local swelling, prolonged pain, or a hard lump that persists past 48 hours is worth mentioning at your next clinic appointment.

When patients ask when do Ovidrel side effects start, the honest answer is "if they start at all, usually within 24 hours, and they peak around the time the follicle is rupturing." If you feel nothing, that does not mean the trigger did not work. The shot can be entirely silent and still produce ovulation on schedule.

When to call the clinic

The trigger shot is well tolerated in oral medication cycles, where typically only one or two follicles have been recruited. The signs to watch for, and the ones that warrant a call rather than a wait-and-see, are:

• Rapid abdominal distension with weight gain over a day or two
• Severe abdominal pain, especially with nausea or vomiting
• Sharply reduced urine output
• Calf swelling, redness, or pain in one leg
• Sudden shortness of breath or chest pain
• Significant injection-site reaction, expanding redness, fever, or pus

The first four point toward ovarian hyperstimulation syndrome (OHSS), which is the clinical condition that develops when the ovaries over-respond and shift fluid out of the bloodstream into the abdomen.⁶ OHSS is uncommon in oral medication cycles. It is more of a concern in IVF stim cycles where many follicles are recruited. Your RE will have looked at the number of mature follicles on your pre-trigger scan and would not have triggered if the count looked dangerous. Still, if any of the above happen, call.

The calf and shortness-of-breath symptoms are clot warning signs. Pregnancy hormones, including the trigger shot itself, slightly raise clot risk, and any new one-sided leg symptom or sudden breathlessness needs immediate evaluation.

For everything else, mild bloating, twinges, breast tenderness, mood changes, the answer is to ride it out for 2 to 3 days and call only if it gets worse.

Ovidrel versus urinary hCG, in practice

If your clinic uses Novarel or Pregnyl instead of Ovidrel, you are getting the same biological signal, just in a different package. The dose is measured in IU rather than micrograms (usually 5,000 to 10,000 IU), and the injection requires mixing a powder with a sterile diluent before drawing it into a syringe. The needle is sometimes intramuscular rather than subcutaneous, which means it goes deeper, into the muscle of the upper outer buttock or thigh.

I have prescribed both and have not seen any meaningful difference in cycle outcomes. The trial evidence agrees: pregnancy rates after recombinant hCG (Ovidrel) and urinary hCG (Novarel, Pregnyl) are essentially the same.² If cost or insurance coverage is shaping which one you get, the answer is to take whichever your clinic prescribes and not worry about the formulation.

What happens after the shot

From the moment the trigger is injected, the cycle runs on a known clock. Roughly 36 to 40 hours later, ovulation occurs.³ If you are doing IUI, that is typically scheduled 24 to 36 hours post-trigger so the washed sperm is in the uterus just before the egg arrives. If you are doing timed intercourse, the window starts the night of the trigger and runs through the following 48 hours.

The trigger shot itself will be detectable on a home pregnancy test for the next 7 to 14 days, because the drug is hCG, and that is what the test reads.⁴ This is the source of countless faint-line stories on fertility forums. I cover the testing-out-the-trigger question in detail in a dedicated post, but the short version is that any positive result in the first week after the trigger is the shot, not pregnancy. The blood beta-hCG draw your clinic schedules at 14 days post-trigger is the reliable test.

About 7 days after the trigger, some patients have a progesterone draw to confirm ovulation actually happened. A level above 10 ng/mL is generally reassuring; below that, your RE may want to repeat the scan or adjust the next cycle.

What's next

• If you have not yet read the foundational explainer: The HCG Trigger Shot: What It Does and Why You Take It
• If you took the shot tonight and need to plan timing: When to Time Sex or IUI After Trigger Shot
• If you are tempted to test early: Trigger Shot False Positives on Pregnancy Tests
• If this is your first IUI: IUI Explained

Sources

1. U.S. Food and Drug Administration. Ovidrel (choriogonadotropin alfa) Prescribing Information. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020726
2. Driscoll GL, Tyler JPP, Hangan JT, Fisher PR, Birdsall MA, Knight DC. A prospective, randomized, controlled, double-blind, double-dummy comparison of recombinant and urinary HCG for inducing oocyte maturation and follicular luteinization in ovarian stimulation. Human Reproduction 2000;15(6):1305-1310. https://doi.org/10.1093/humrep/15.6.1305
3. Practice Committee of the American Society for Reproductive Medicine. Evidence-based treatments for couples with unexplained infertility: a guideline. Fertility and Sterility 2020;113(2):305-322. https://doi.org/10.1016/j.fertnstert.2019.10.014
4. Damewood MD, Shen W, Zacur HA, Schlaff WD, Rock JA, Wallach EE. Disappearance of exogenously administered human chorionic gonadotropin. Fertility and Sterility 1989;52(3):398-400. https://pubmed.ncbi.nlm.nih.gov/2670598/
5. Chan CC, Ng EH, Tang OS, Yeung WS, Ho PC. A prospective, randomized, double-blind study to compare two doses of recombinant human chorionic gonadotropin in inducing final oocyte maturity and the hormonal profile during the luteal phase. Journal of Clinical Endocrinology & Metabolism 2005;90(7):3933-3938. https://doi.org/10.1210/jc.2004-2169
6. Practice Committee of the American Society for Reproductive Medicine. Prevention and treatment of moderate and severe ovarian hyperstimulation syndrome: a guideline. Fertility and Sterility 2016;106(7):1634-1647. https://doi.org/10.1016/j.fertnstert.2016.08.048