Gonal-F is a lab-made version of follicle-stimulating hormone (FSH), the same hormone your brain naturally releases to grow eggs in your ovaries each month. In IVF, it’s injected daily to push your ovaries into producing multiple mature eggs instead of the single egg your body would typically select. Most patients inject it for roughly 8 to 10 days before their eggs are ready for retrieval.
How Gonal-F Works in Your Ovaries
Every menstrual cycle, your pituitary gland releases FSH to coax a batch of tiny follicles (fluid-filled sacs that each contain an egg) into growing. Normally, only one follicle wins the race, matures fully, and ovulates. The rest die off. Gonal-F floods your system with far more FSH than your body would produce on its own, which rescues those follicles that would otherwise be lost and keeps them all growing simultaneously.
At the cellular level, FSH locks onto receptors on the granulosa cells that surround each egg. This triggers a chain reaction inside those cells: they ramp up estrogen production, multiply, and send survival signals that protect the developing eggs from the natural die-off process. The same signaling also switches on receptors for another key hormone, LH, which becomes critical later when it’s time to trigger final egg maturation. In short, Gonal-F doesn’t create new eggs. It saves the ones your body already recruited that cycle and pushes them all toward maturity at the same time.
Where It Fits in the IVF Timeline
Gonal-F is the backbone of the “stimulation phase,” which typically begins in the first few days of your cycle. You’ll inject it subcutaneously (just under the skin of your belly or thigh) once a day, at roughly the same time each day. In a large dataset of IVF cycles, the average stimulation lasted about 9 days, though your clinic may adjust that window from 7 to 12 days depending on how your follicles respond.
During stimulation, you’ll visit the clinic every two to three days for blood draws and transvaginal ultrasounds. Your care team is watching two things: how many follicles are growing and how big they are. Once the leading follicles reach about 18 to 21 millimeters in diameter, you’ll be told to take a “trigger shot” to finalize egg maturation. Egg retrieval follows roughly 36 hours later.
Most IVF protocols also pair Gonal-F with a second medication that prevents you from ovulating too early. Without that suppression, your body could release the eggs before the retrieval procedure.
Typical Dosing and What Determines Yours
Starting doses generally fall between 150 and 300 IU per day. For a first cycle in someone with normal ovarian reserve, 150 to 200 IU per day is the most common starting point. If you’re older, have a low antral follicle count, elevated baseline FSH levels, or low AMH (a hormone that reflects your remaining egg supply), your doctor will likely start higher, often 300 IU per day. The recommended ceiling most clinicians follow is 300 to 450 IU per day.
Your dose isn’t locked in for the entire stimulation. Based on how your follicles look at monitoring appointments, the clinic can raise or lower the dose partway through. This fine-tuning is one of the most important parts of the cycle, because the goal is enough follicles to give you good odds without pushing your ovaries into overdrive.
How Many Eggs to Expect
In a German study comparing stimulation medications, patients using Gonal-F retrieved an average of about 10 eggs per cycle. That number varies widely depending on age, ovarian reserve, and dose. Some patients produce 5 or 6 eggs, others 15 or more. Not every egg retrieved will be mature, and not every mature egg will fertilize or develop into a viable embryo, so a higher starting number gives you more opportunities at each stage.
Compared to older, urine-derived FSH products, Gonal-F tends to recruit more follicles and requires less medication per egg retrieved. That said, the clinical pregnancy rates between the two types of FSH are broadly equivalent, so the choice often comes down to your clinic’s protocol, cost, and convenience.
Common Side Effects
The most frequent side effects are local injection site reactions: redness, mild swelling, stinging, or itching where the needle went in. These tend to improve as you get used to the injections. Hormonal side effects are also common and expected, since your estrogen levels are climbing rapidly. You may notice bloating, breast tenderness, mood swings, headaches, acne, or oily skin. Many patients describe feeling “full” or heavy in the lower abdomen as their ovaries enlarge.
These side effects are a normal part of stimulation and usually resolve within a week or two after egg retrieval. If bloating becomes severe, or you experience sharp abdominal pain, nausea, vomiting, or difficulty breathing, contact your clinic immediately, as these can signal ovarian hyperstimulation syndrome.
Ovarian Hyperstimulation Syndrome (OHSS)
OHSS is the most significant risk of any FSH-based stimulation. It happens when the ovaries overreact and swell, leaking fluid into the abdomen and sometimes the chest. In a systematic review covering over 5,000 treatment cycles with Gonal-F, about 5% of cycles involved some degree of OHSS. Most cases were mild or moderate, involving bloating, discomfort, and temporary weight gain that resolved on its own. Severe OHSS, which can require hospitalization, occurred in roughly 0.2% of cycles.
Certain factors raise your risk: being under 30, having polycystic ovary syndrome (PCOS), a high antral follicle count, or producing a very high number of eggs. Modern IVF protocols have gotten much better at reducing severe OHSS through dose adjustments, different trigger shot options, and “freeze-all” strategies where embryos are frozen instead of transferred in the same cycle, giving your ovaries time to settle down.
Using and Storing the Gonal-F Pen
Gonal-F comes in a prefilled injection pen (the Redi-ject) with a dial that lets you set your exact dose. Before first use, store the pen in the refrigerator between 36°F and 46°F. You can also keep an unopened pen at room temperature (up to 77°F) for up to 3 months. Once you’ve used a pen for the first injection, it stays good for 28 days whether refrigerated or kept at room temperature. Never freeze it.
Each pen contains more medication than a single dose, so you’ll use the same pen across several days. Your clinic or pharmacist will show you how to attach the needle, dial the dose, and inject. Most patients find the needle surprisingly small and the injection relatively painless, especially compared to what they expected.
How Gonal-F Compares to Other Stimulation Drugs
Gonal-F is a recombinant product, meaning it’s manufactured in a lab using genetically engineered cells rather than extracted from human urine. This gives it a consistent composition from batch to batch. Older urinary-derived products contain a slightly different mix of FSH variants that clear from your body more slowly, which can mean fewer follicles but potentially slightly different egg quality characteristics. In head-to-head comparisons, pregnancy rates are similar between the two categories, so the practical differences for most patients are small.
Other brand-name recombinant FSH products (like Follistim) use the same active ingredient and work the same way. The choice between them typically comes down to insurance coverage, pharmacy availability, and which pen device your clinic prefers.