IVF injections are hormone medications given by needle (usually into the belly or thigh) to stimulate your ovaries to produce multiple mature eggs in a single cycle. In a natural menstrual cycle, your body releases just one egg. These injections override that process so your fertility team can retrieve several eggs at once, improving the chances of creating viable embryos. Most people give themselves these shots at home, daily, for 8 to 13 days.
There are several categories of injections used at different stages of an IVF cycle, each with a distinct job. Here’s what each one does and what the experience looks like.
Stimulation Injections: Growing Multiple Eggs
The core of any IVF cycle is the stimulation phase, where you inject gonadotropins, hormones that act directly on the ovaries to grow follicles (the fluid-filled sacs that each contain an egg). The two key hormones are follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which your body produces naturally in small amounts but not enough to mature multiple eggs at once.
Common brand names include Gonal-F and Follistim, which contain FSH only, and Menopur, which combines FSH and LH. Your doctor selects one or a combination based on your age, body weight, hormone levels, and how your ovaries have responded in previous cycles. Typical starting doses range from 100 to 300 international units per day, with lower doses generally preferred when possible. Research on over 8,700 IVF cycles found that starting doses above 200 IU were actually associated with fewer usable embryos, so more medication doesn’t necessarily mean better results.
These injections are subcutaneous, meaning the needle goes just under the skin rather than into muscle. Most people use the lower abdomen, alternating sides each day. The needles are short and thin, similar to what someone with diabetes would use for insulin. You’ll go to your clinic every two to three days during stimulation for blood draws and ultrasounds so your team can track how your follicles are growing and adjust your dose if needed.
Suppression Injections: Preventing Early Ovulation
While stimulation injections are growing your eggs, there’s a risk your body will ovulate on its own before your doctor can retrieve them. A second category of injections prevents this by blocking the hormonal signal from your brain that triggers ovulation.
There are two approaches. The more common modern protocol uses antagonist medications (brand names cetrorelix or ganirelix), which directly block the hormone receptors in your pituitary gland. These are typically added partway through your stimulation cycle, once your largest follicle reaches about 14 millimeters, and continue daily until the trigger shot. They work quickly and are straightforward to use.
The older approach uses agonist medications (such as triptorelin or leuprolide), which initially overstimulate and then exhaust those same receptors, effectively shutting down your body’s ovulation signal. These start earlier, sometimes in the cycle before your IVF cycle even begins, and require a longer course of injections. Both approaches are effective, but antagonist protocols involve fewer total injection days and have become the standard at most clinics.
The Trigger Shot: Timing the Egg Retrieval
Once your follicles reach the right size, you’ll take one final injection called the trigger shot. This replaces the natural LH surge that would normally cause ovulation, pushing your eggs through their last stage of maturation so they’re ready for retrieval. Timing is precise: most clinics schedule retrieval exactly 36 hours after the trigger, so you’ll be told the exact hour to inject.
The most traditional trigger is human chorionic gonadotropin (hCG), sold under names like Pregnyl or Ovidrel. Some protocols use leuprolide (Lupron) as the trigger instead, particularly for patients at higher risk of ovarian hyperstimulation. In some cases, doctors prescribe both together as a “co-trigger” to combine the benefits of each. Unlike your daily stimulation shots, the trigger is a single injection, and missing it or taking it at the wrong time can derail the entire cycle.
Progesterone After Retrieval
After egg retrieval, many patients begin progesterone to prepare the uterine lining for embryo transfer. Progesterone is sometimes given as a vaginal suppository or oral medication, but intramuscular injections are also common. These go into the upper outer area of the buttock using a longer needle, which many people find more uncomfortable than the subcutaneous stimulation shots. Progesterone injections typically continue daily for several weeks, often through the first 8 to 12 weeks of pregnancy if the transfer is successful.
What the Injections Feel Like
The subcutaneous shots used during stimulation are the mildest. Most people describe a brief pinch or sting that fades within seconds. Injection sites can become slightly bruised, red, or itchy over the course of a cycle, and rotating sides helps minimize this. Icing the area beforehand can reduce discomfort.
Intramuscular progesterone shots are a different experience. The needle is longer, the oil-based medication is thick, and the injection site can develop soreness or hard lumps over time. Warming the vial between your hands before injecting and applying a heating pad afterward can help the medication absorb more evenly.
Beyond the injection sites themselves, the hormones cause systemic side effects. Bloating, mood swings, headaches, fatigue, and breast tenderness are all common during stimulation. Your ovaries physically enlarge as follicles grow, which can create a feeling of heaviness or pressure in your pelvis. These effects resolve after the cycle ends, though it can take a week or two.
Ovarian Hyperstimulation Syndrome
The most significant risk of IVF injections is ovarian hyperstimulation syndrome (OHSS), where the ovaries overrespond and swell painfully. Symptoms typically begin within a week of the trigger shot and range from mild to severe.
Mild cases involve bloating, nausea, diarrhea, and tenderness near the ovaries. Most people with mild OHSS can manage symptoms at home and recover within a few days. Severe OHSS is less common but more serious, causing rapid weight gain (more than 2.2 pounds in 24 hours), persistent vomiting, shortness of breath, decreased urination, and in rare cases blood clots. Severe symptoms require medical attention and sometimes hospitalization.
Your clinic monitors for OHSS risk throughout the cycle. If your estrogen levels rise too quickly or too many follicles develop, your doctor may lower your medication dose, switch to a Lupron trigger instead of hCG, or recommend freezing all embryos and delaying transfer to a later cycle when your body has recovered.
Storing Your Medications
IVF medications can be expensive, and improper storage can ruin them. The general rule: unmixed (powdered) vials are stable at room temperature. Once you mix a powder with its liquid solution, it needs to go in the refrigerator and is typically good for about 30 days. Pre-filled pen cartridges like Follistim AQ and Gonal-F AQ need refrigeration at all times, both before and after first use. Progesterone suppositories also require refrigeration since they’re wax-based and will melt at room temperature.
If you’re traveling during a cycle, a small insulated cooler with ice packs keeps medications at the right temperature. Avoid letting any refrigerated medication freeze, which can damage its potency just as much as heat.