How is Follistim stored?

Storage varies by device and whether it is opened or unopened, so check the leaflet in the box and ask your clinic if unsure.

Is the pen device reusable?

Some Follistim pen devices are used for multiple injections from one cartridge. Your clinic nurse will show you how the specific device you have been given works.

What if I am unsure I injected the full dose?

Contact your clinic to check rather than repeating the injection or guessing.

Can it be taken with other stimulation medicines?

Some protocols combine it with other medicines. Only take what your clinic has specifically prescribed for you.

Follicle stimulating hormone (FSH) injection

Follistim

Also known as Follitropin beta, Puregon (same active ingredient, different brand name)

Written by Zayn Miah & R KhanomLast updated 17 September 2026Not clinically reviewed

Follistim is a lab-made form of follicle stimulating hormone, given by injection under the skin, usually with a pen device.

Why it may be used

It is used during IVF stimulation to encourage several follicles to grow at the same time, increasing the number of eggs that may be available at retrieval compared with a natural cycle.

Where it fits in a cycle

It is generally given during the stimulation phase of a cycle, with dose and duration decided by your clinic and monitored through ultrasound scans and blood tests as the cycle progresses.

Side effects listed in the patient leaflet

Injection site redness, swelling or bruising
Headache
Abdominal bloating or discomfort
Nausea
Breast tenderness
Mood changes
Ovarian enlargement during treatment

When to ring the clinic

•Fast-developing abdominal swelling or bloating
•Severe abdominal or pelvic pain
•Difficulty breathing
•A marked drop in how much urine you are passing
•Sudden weight gain or signs of infection at an injection site

Questions people ask

How is Follistim stored?: Storage varies by device and whether it is opened or unopened, so check the leaflet in the box and ask your clinic if unsure.
Is the pen device reusable?: Some Follistim pen devices are used for multiple injections from one cartridge. Your clinic nurse will show you how the specific device you have been given works.
What if I am unsure I injected the full dose?: Contact your clinic to check rather than repeating the injection or guessing.
Can it be taken with other stimulation medicines?: Some protocols combine it with other medicines. Only take what your clinic has specifically prescribed for you.

Safety

This page gives general information only and is not a substitute for advice from your fertility clinic.
Doses and timing must come from your own clinic's written instructions, not from what others have used.
The patient information leaflet included with the medicine is the authoritative reference for this product.
Tell your clinic about any other medicines, allergies or medical conditions before starting.

Sources

Patient information leaflets and product characteristics, electronic medicines compendium (emc). Link checked 17 September 2026.
IVF: what is IVF and how does it work?, HFEA (UK fertility regulator). Link checked 17 September 2026.

Written by patients, not clinicians. This page has not yet been reviewed by a named fertility professional, so it explains published guidance and points you to the original source instead of giving medical advice. It is not medical advice. Decisions about your treatment belong with your own clinic. Read our editorial policy and corrections policy.