Olaparib Side Effects: — What to Watch For and When to Call

Nausea is among the most commonly reported side effects of olaparib and is often most noticeable in the first few weeks of treatment. Taking your tablets with food can help reduce it. Small, frequent meals tend to be better tolerated than large ones. If nausea is severe, if you are vomiting more than twice a day, or if you cannot keep your tablets or fluids down, call your team the same day. Your team can prescribe anti-nausea medication if it is not already part of your plan — it is worth asking rather than managing without.

Fatigue is very commonly reported on olaparib. It can begin early in treatment and may persist, though many patients find it settles to a manageable level after the first weeks. Pacing activity — doing important things when your energy is highest and resting before you become exhausted — works better than pushing through. Tell your team if fatigue is severe, suddenly worsens, or stops you from managing basic daily tasks. Worsening fatigue can sometimes indicate developing anaemia rather than a direct drug effect, and anaemia is detectable on a blood test and treatable.

Olaparib can lower the red blood cell count, a condition called anaemia. Mild anaemia tends to cause noticeable tiredness and can worsen breathlessness on exertion. Your regular blood tests will pick it up before it becomes severe. Call your team the same day if you feel breathless after very little effort, feel noticeably pale or dizzy on standing, or have any chest discomfort. Severe anaemia may need a blood transfusion, a dose reduction, or a temporary pause — your team will decide based on your result and how you feel.

Olaparib can lower the white cell count, reducing your body's ability to fight bacterial infection. This is usually caught by routine blood monitoring before you develop symptoms. The single most important rule is that any fever during treatment means calling your team the same day — do not wait for your next appointment or for other symptoms to appear alongside it. Neutropenia with fever can become serious within hours. Your team will give you a temperature threshold and a contact number when you start treatment; keep both somewhere accessible at all times.

Platelets are the cells that help blood clot when you are injured. Olaparib can lower platelet count, which your routine blood tests monitor. Mild thrombocytopenia often has no obvious symptoms. Call your team if you notice bruising that appears without injury, small red or purple spots under the skin, prolonged bleeding from a minor cut, or any bleeding that is unusual for you. Heavy or spontaneous bleeding means going to hospital the same day rather than waiting for a callback — do not try to manage it at home.

A very small number of patients who take olaparib develop myelodysplastic syndrome (MDS) or acute myeloid leukaemia (AML) — both are conditions affecting the blood-forming cells in the bone marrow. This is a recognised but rare risk, noted in guidance from NCCN and ESMO. It tends to appear later in the treatment course rather than in the first weeks. Your blood count monitoring is designed partly to detect these changes early. Tell your team promptly if your blood results have been persistently abnormal, if you are developing infections more often than before, or if you feel something has shifted. We do not yet have a reliable way to predict who is at risk, which is why monitoring is the protective measure — not skipping tests is the most practical thing you can do.

Some people on olaparib find that food tastes different — metallic, bland, or simply less appealing than usual. This is called dysgeusia and tends to be more disruptive than dangerous. Cold or room-temperature foods are sometimes better tolerated than hot ones when taste is affected. If reduced appetite is causing weight loss or regular missed meals, tell your team — a referral to a dietitian is a practical step that many people find genuinely useful. Taste changes often improve but can persist, and addressing them early is better than struggling through.

Headaches and dizziness are reported by some people on olaparib. Mild headaches often settle with adequate hydration and rest. If dizziness is a problem, stand up slowly from sitting or lying down, as it is most commonly positional. Persistent or severe headache, a sudden severe headache unlike any you have had before, or dizziness that is worsening or affecting your ability to stand safely is worth reporting to your team promptly. Dizziness can sometimes reflect anaemia or low blood pressure — both of which your team can check and address.