At a glance

Triptorelin is a medicine used in specialist cancer care. Brand names include Decapeptyl SR, Gonapeptyl Depot, Trelstar. The practical instructions depend on the exact prescription and product supplied.

Your prescription and the instructions for your own product take priority over a general guide. Keep the medicine leaflet as well as your treatment plan, especially if the brand or formulation changes.

You do not need to remember every possible side effect. Start with the administration instructions and the section on urgent help. Most people experience only some of the effects described here. Tell your team about difficulties early: supportive treatment, a planned pause or a different medicine may make treatment easier to continue.

How it works

Triptorelin is a GnRH agonist that suppresses testosterone or ovarian oestrogen after an initial hormone stimulation. It is supplied in depot formulations whose strength, route and duration depend on the product and treatment purpose.

Is this treatment suitable for me?

The team chooses a formulation for the intended hormone suppression. If an aromatase inhibitor is used with ovarian suppression, the ovaries must be adequately suppressed before that tablet starts. Longer-acting products used in another setting are not automatic substitutes.

Your oncologist considers the biology of the cancer, treatments already received, other illnesses and your preferences. The aim may be to reduce the chance of cancer returning, control cancer that is present, or relieve symptoms. Ask which aim applies to you and how benefit will be assessed. The same medicine can be used for different lengths of time in different treatment plans.

A brand name alone does not tell you whether a medicine is suitable. The dose, formulation and other medicines in the plan also matter. Discuss the possible benefits and risks with your care team.

Before treatment

Discuss heart disease, diabetes, abnormal rhythms, depression, seizures, fractures and urinary or spinal symptoms. Before ovarian-suppression treatment, mention unusual vaginal bleeding and possible pregnancy. Ask for the exact product name and next appointment date.

Bring an up-to-date list of prescription medicines, pharmacy medicines, supplements and traditional or herbal remedies. Include medicines used only occasionally, creams containing hormones, and anything recently stopped. Mention previous allergies and describe what happened, rather than only naming the drug. Your pharmacist can check the whole list together.

Tell the team about any planned operation, dental procedure, travel or difficulty attending appointments. Discuss costs and supply before the first dose if obtaining regular refills may be difficult. Agree who will arrange repeat prescriptions and tests. Keep your own hospital's daytime and out-of-hours contact details where you and a caregiver can find them quickly.

For ovarian-suppression treatment, pregnancy must be excluded before starting. Report unexplained vaginal bleeding so that it can be assessed before treatment.

How to take or receive treatment

Decapeptyl SR 3 mg is given intramuscularly every four weeks in an appropriate monthly plan. Other Decapeptyl depot strengths have longer intervals. Trelstar formulations use 3.75 mg every four weeks, 11.25 mg every 12 weeks or 22.5 mg every 24 weeks in their labelled setting. Gonapeptyl presentations have their own instructions. Milligram numbers alone do not establish equivalence.

For ovarian suppression with an aromatase inhibitor, UK Decapeptyl information specifies starting triptorelin at least six to eight weeks beforehand, with at least two monthly injections and confirmation of suppression. Follow the start date given by the specialist. If an injection is missed, contact the clinic promptly.

Check the date of the next appointment before leaving the clinic. An injection described as monthly may have a specific number of weeks or calendar-month interval; use the date your team gives you. Contact the clinic promptly if an appointment is missed or needs changing. Do not arrange an extra dose, substitute another depot strength or change the interval yourself.

Tell the nurse about blood thinners, unusual bruising, an infection near the planned injection site or a previous injection reaction. The preparation and route are specific to the product. These depot injections or implants are prepared and given by a healthcare professional.

Usually the clinic stores and prepares the medicine. If you must collect or transport it, ask the dispensing pharmacy how to store and transport it, and keep their instructions handy. Do not assume all injections need the same refrigeration.

Use a calendar or a phone reminder that records what was actually taken or given. A tick made after a dose is more useful than one made in advance. If someone helps with medicines, agree who records each dose so it is not accidentally repeated. Keep the drug name, strength and current instructions together; an old prescription may no longer describe your current dose.

Contact the treating team if a supply problem or illness is likely to interrupt treatment. Do not stretch the supply by taking smaller doses or lengthening intervals yourself. If you receive too much medicine, seek urgent advice and have the packaging and dose times available. Do not induce vomiting.

Monitoring your treatment

Hormone tests may assess testosterone or ovarian suppression, with PSA or other cancer-response assessments as appropriate. Monitor bone health, glucose, cardiovascular risks and mood. Returning periods or bleeding after suppression is established needs review.

Monitoring has two purposes: checking whether treatment is helping and detecting problems that may be silent at first. Your schedule depends on the medicine, any partner treatment and your general health. Ask which results need to be reviewed before the next prescription or injection, and who will contact you if a result is abnormal.

Record symptoms that affect eating, walking, sleep or daily activities, along with when they began. Bring this record to appointments. A single symptom or blood result rarely explains the whole picture; the team may compare trends, examination findings and scans. Feeling well is welcome, but it does not remove the need for planned monitoring.

If you have a heart-rhythm risk, the team may check an ECG and blood electrolytes before and during treatment, and correct abnormal electrolyte levels.

With monthly Decapeptyl plus an aromatase inhibitor, UK instructions specify checking follicle-stimulating hormone (FSH) and oestradiol before starting the tablets and every three months during combination treatment. Assess bone density before breast-cancer treatment, particularly with additional osteoporosis risks. During testosterone suppression, the team should also review blood lipids and glucose or HbA1c, and assess anaemia when appropriate.

Common side effects

Effects to discuss with your team

Hot flushes, sweating, fatigue, sexual changes, mood symptoms and local injection discomfort can occur. Initial spotting is possible when ovarian hormones change. Tell the team if symptoms interfere with sleep, relationships or daily activities.

These medicines change the signals that control hormone production. After an initial stimulation, continuous treatment suppresses the signal, lowering testosterone or ovarian oestrogen according to the organs present. Early symptoms can therefore differ from those experienced after suppression is established. A temporary rise in hormones can cause a flare, but new severe pain or neurological symptoms must never simply be labelled a harmless flare.

Lower sex-hormone levels can cause hot flushes, night sweats, reduced sexual interest, fatigue and mood changes. Vaginal dryness or erection difficulties may also occur. Cooling measures, a regular sleep routine and tailored activity can help some people. Persistent symptoms deserve treatment rather than silent endurance. Do not start hormone replacement or testosterone supplements without the cancer team's agreement.

Longer treatment can reduce bone density and alter body composition. Your team may assess fracture risk and discuss a bone-density scan, vitamin D, calcium intake and medicines to protect bone where appropriate. Blood pressure, weight and blood sugar may need review, particularly when testosterone is suppressed. Report severe depression, new visual symptoms or a sudden unusual headache promptly.

When used for ovarian suppression with an aromatase inhibitor, reliably low oestrogen is essential. The team may check hormone blood tests before the partner medicine starts and during treatment. Stopping periods does not by itself prove adequate suppression or provide reliable contraception. Report returning periods or persistent bleeding and do not let injection appointments lapse.

Making symptoms easier to manage

Tell the team which symptom is causing the most difficulty. Describe its effect on ordinary tasks: for example, whether pain prevents dressing or tiredness stops you preparing food. This helps the team choose practical support and judge whether treatment needs adjustment. Avoid waiting until the next routine visit if symptoms are worsening.

For mild nausea, try smaller meals and regular sips of fluid, following any food rule for the medicine. Ask about an anti-sickness medicine if needed. Repeated vomiting, inability to keep fluids down or very little urine needs prompt advice. If you have been told to restrict fluids for another illness, use that plan rather than forcing extra drinks.

Energy and emotional wellbeing

Pace demanding activities and allow rest, but keep some gentle movement in your day if you can. Persistent exhaustion deserves assessment; poor sleep, anaemia, low mood and other illnesses may contribute. Tell the team about persistent anxiety, sadness or loss of interest. If you feel at risk of harming yourself, seek emergency help and ask someone to stay with you.

Important side effects

The effects below are important because they may require tests or a change in treatment. They are not a prediction that you will develop them. New symptoms can also come from the cancer or an unrelated illness. Reporting them promptly allows the team to work out the cause; do not assume that everything is a routine treatment effect.

Initial flare, bone thinning, glucose changes, heart rhythm problems, seizures and severe skin reactions are important risks. Current Trelstar information includes serious blistering skin reactions. Rare pituitary complications can cause sudden severe headache and visual symptoms.

Metabolic changes can include raised blood fats and fatty liver disease. These may develop without obvious symptoms, so planned blood tests remain important.

When to get urgent help

New severe back pain with leg weakness or bladder/bowel changes, urinary retention, seizure, severe chest pain or stroke symptoms requires emergency assessment. Seek urgent care for a spreading blistering rash with fever or mouth sores, or a sudden severe headache with visual change.

Get emergency help immediately for severe breathing difficulty, swelling of the tongue or throat, collapse, a seizure, severe chest pain, or signs of a stroke such as a drooping face, new arm weakness or difficulty speaking. Do not drive yourself if you are faint, confused or seriously unwell, and do not wait for an oncology callback before seeking emergency care.

Contact your oncology team the same day for repeated vomiting, dehydration, new jaundice, a rapidly worsening rash, or a sudden major change in how you feel. Fever with shaking chills or feeling acutely unwell also needs prompt advice, particularly if you receive another treatment that can lower white blood cells. Follow the temperature threshold and emergency instructions given for your complete regimen.

When asking for help, give the medicine name, last dose or injection date, other cancer treatments and main symptoms. Mention any blood thinner or steroid. If you cannot reach the team and the problem is urgent, use your hospital's emergency service rather than waiting for the next appointment.

Do not receive another injection until a suspected severe skin reaction has been assessed. A confirmed severe reaction can mean treatment must be stopped permanently.

Other medicines and vaccinations

Review medicines affecting QT rhythm, seizure risk, prolactin or bone strength. Do not add HRT or testosterone supplements without the oncology team's agreement. Partner endocrine treatments have their own interaction and contraception instructions.

Ask the oncology pharmacist to check new medicines before you start them, including antibiotics prescribed elsewhere. Do not stop essential treatment for another illness on your own. If an interaction is possible, the prescribers can choose an alternative, adjust a dose or arrange monitoring. Herbal products labelled natural can still alter drug levels or have hormone-like effects.

Vaccination advice depends on your complete treatment plan. Hormone treatment alone does not automatically mean that every vaccine is unsuitable. Ask about influenza, COVID-19 and other recommended vaccines; live vaccines need a specific check if you also receive chemotherapy, an immune-suppressing medicine or certain doses of steroid. Tell the vaccination service all the treatments you receive.

Everyday life

Food and movement

Aim for regular meals with enough protein and a varied range of foods that you can tolerate. Tell the team about unplanned weight loss, rapid weight gain or difficulty eating. A dietitian can adapt advice to diabetes, kidney problems, bowel symptoms or a restricted appetite. Do not start a restrictive diet or high-dose supplement as a substitute for treatment.

Choose activity that suits your strength and balance. Short walks or gentle exercises may be easier to sustain than occasional strenuous sessions. If cancer affects your bones, or you have osteoporosis, ask which movements and resistance exercises are safe before starting a new programme. New focal bone pain should be assessed rather than exercised through.

Work and travel

Many people continue some usual activities, but flexibility helps while you learn how treatment affects you. Discuss rest breaks, shorter hours or help with physically demanding work if needed. Avoid driving or operating machinery when dizzy, sleepy, confused or affected by visual symptoms. Follow any additional driving advice after a seizure or loss of consciousness.

Plan travel around prescriptions, injections and tests. Carry an up-to-date medicine list and enough supply for the agreed trip, with advice about storage and time-zone changes. For long journeys, discuss mobility and your individual clot risk. Do not start aspirin or a blood thinner simply because you are travelling.

Relationships and support

Changes in energy, body image or sexual function can affect relationships. You can ask for help privately, with or without a partner present. There may be practical measures or specialist support for discomfort and intimacy. A caregiver can help record symptoms and organise appointments while leaving treatment decisions and personal information under your control.

Fertility, pregnancy and breastfeeding

Triptorelin does not reliably prevent pregnancy. Use agreed non-hormonal contraception during ovarian-suppression treatment and afterwards until the team confirms it may stop; product advice includes continuing until periods return, with formulation-specific precautions. Do not breastfeed during treatment. Other anticancer medicines may require longer precautions.

Tell the team before treatment if having children in the future matters to you. Fertility preservation needs discussion before exposure where possible. Reduced fertility is not the same as reliable contraception, and an absence of periods or reduced sexual function does not prove that pregnancy is impossible.

Ask your team which contraception to use and how long to continue it, taking account of every medicine in your regimen. A partner drug may require a longer precaution period than this medicine alone. If pregnancy is suspected in you or a partner during a risk period, contact the treating team promptly for individual advice. Do not make pregnancy or breastfeeding decisions from a generic time interval without checking your own treatment plan.

After treatment

Do not discontinue triptorelin while continuing an aromatase inhibitor without a coordinated plan. Hormonal recovery varies and can take time after a depot wears off. Confirm continuing bone-health care and follow-up after the last dose.

Before a planned stop, confirm which medicines end, which continue, and when the next review is due. Return unused medicine through the pharmacy's recommended route; do not give it to another person. Keep a record of the last dose and any side effects that still need follow-up.

Changes caused by treatment may settle gradually, and some need ongoing support. Report persistent symptoms or new problems after treatment rather than assuming they will disappear on their own. Continue the agreed follow-up and screening plan. If treatment is being changed, ask your team to help you update your treatment schedule so that old and new instructions are not accidentally combined.

Common questions

Why do different triptorelin brands have different milligram doses?

Depot products differ in formulation and release characteristics. The nominal strength does not make two preparations directly interchangeable. The prescriber and pharmacist must check the exact product, purpose, route and interval before a change.

Can I start the aromatase inhibitor on the day of my first injection?

Use the date given by your team. Some ovarian-suppression protocols require six to eight weeks and at least two monthly injections before the aromatase inhibitor starts, with hormone checks. Starting early without adequate suppression can undermine the intended treatment.

What if periods return while I am on treatment?

Tell the team promptly, especially if an aromatase inhibitor is part of the plan. Returning bleeding may prompt assessment of ovarian suppression and other causes. Do not assume that stopping and restarting injections yourself will solve it.

Can I keep the tablets but stop the injections because of hot flushes?

Not without specialist review. When tablets depend on ovarian suppression, the treatments work as a planned combination. The team can help manage symptoms or discuss alternatives while preserving a coherent treatment plan.

Is this the same as chemotherapy?

It is a hormonal or hormone-related treatment, with a different way of working from conventional chemotherapy. It still needs careful prescribing and monitoring. If chemotherapy or a targeted medicine is part of your plan as well, read the information for that medicine because the combined treatment may have additional risks.

How will I know whether treatment is helping?

Your team will explain which symptoms, blood tests, examinations or scans are useful in your situation. Improvement may take time, and some treatments aim to prevent future problems rather than produce a change you can feel. Keep review appointments even when you feel well.

Does having few side effects mean the medicine is not working?

No. Side effects are not a reliable measure of benefit. People can respond to treatment without feeling particularly different. Equally, having troublesome effects does not prove that the cancer is responding. Decisions should use your clinical assessments and test results.

Can I take a break when I feel tired?

Do not create your own breaks or change the dose. Contact the team about fatigue and explain how it affects your day. They may look for another cause, offer support or prescribe a planned adjustment. A supervised change can be safer than repeated unrecorded missed doses.

How long will I need this medicine?

The duration depends on the aim of treatment, response and tolerability. Some plans have a proposed end date; others continue while the balance of benefit and side effects remains favourable. Ask when this will be reviewed. Another person taking the same medicine may appropriately have a different schedule.

Can I use herbal or Ayurvedic products alongside treatment?

Show the pharmacist the ingredients and exact product before using it. Products may affect hormone activity, liver function or the way medicines are handled in the body. Different preparations with similar names can contain different ingredients. A claim that a product is natural does not establish that the combination is safe.

Should I stop my usual medicines?

Continue them unless a prescriber tells you otherwise, but arrange a full interaction check. Include occasional painkillers, supplements and any newly prescribed medicine. If an interaction is found, the team can agree a safe change without leaving another illness untreated.

What should I do if I need surgery or dental treatment?

Tell both teams about your cancer medicine well in advance. They may need to consider bleeding, clotting, steroid support, bone-protecting treatment or appointment timing. Do not stop treatment based on a general internet rule. Ask your team when to pause and restart treatment, and keep the instructions handy.

Can someone else manage my medicines for me?

Yes, if you want that support. Agree one shared record of doses and appointments and ask the pharmacist about safe handling. A caregiver should know the urgent symptoms and where to seek help. Do not share this prescription with anyone else, even if their diagnosis sounds similar.

What if I cannot obtain the next supply or attend the clinic?

Contact the treating service before treatment is due where possible. Give the drug name, formulation and date of the last dose. The team can address supply or reschedule safely. Do not substitute another hormone medicine, ration tablets or assume a delayed injection has no consequences.

When should I seek help instead of waiting for my review?

Use emergency care for severe symptoms such as breathing difficulty, collapse, chest pain, stroke symptoms or a seizure. Contact the oncology team promptly for a new or worsening problem that affects normal activities. The urgent-help section gives additional signs especially relevant to this medicine.

Sources and further reading

Information checked against the following sources on 28 September 2026. Product names and instructions can differ between formulations and countries; your treating team should confirm the instructions for your supplied medicine.