Food, Diet and Hydration — During Chemotherapy

Not necessarily. Many people continue to work for at least part of their treatment, particularly those with desk-based or home-based roles. The most common reason for reducing hours is fatigue, which tends to be highest in the days immediately after each infusion and can build across cycles. Scheduling around those peaks — treating infusion day and the days immediately after as rest — allows many people to stay in work through the rest of the cycle. Whether that is possible for you depends on your regimen and your role. Ask your oncologist what to expect from your specific treatment.

No. There is no cancer diet, and no food that treats cancer or makes it grow faster. What matters during chemotherapy is far more ordinary: eating enough to hold your weight, getting enough protein, and drinking enough fluid. People who lose weight and muscle during treatment often tolerate their cycles less well, so the practical goal is to keep eating, in whatever form you can manage on a given day. If you are struggling to eat, ask your team for a referral to an oncology dietitian rather than following advice from relatives or the internet.

Cutting sugar out does not starve a tumour. This is one of the most common beliefs families bring to the clinic, and it causes real harm when it leads someone to eat far less at a point in treatment when they need calories. Your body needs energy to get through chemotherapy and to repair between cycles. A generally balanced diet is sensible for everyone, but there is no reason to eliminate a food group during treatment unless your oncologist or dietitian has told you to — for example, if you also have diabetes that needs managing alongside your chemotherapy.

Your team will give you a target, and it is worth asking for it specifically rather than guessing. Several chemotherapy drugs are cleared through the kidneys, and staying well hydrated helps protect them. Vomiting, diarrhoea and fever all increase how much you need. Some people — particularly those with heart or kidney conditions — are told to limit fluids instead, which is why a general number from the internet is not a safe substitute for your own instruction. Dark urine, passing very little urine, dizziness on standing or a dry mouth that will not settle are all reasons to call your team.

Often it can be adapted, but it needs to be discussed with your oncologist before the fast rather than after. Whether fasting is safe depends on your regimen, which day of the cycle you are on, whether you are taking oral chemotherapy or supportive medicines at fixed times, and how your kidneys are doing. Many people are able to observe part of a fast, or shift it to a different point in the cycle. Bring it up at your next appointment — your team would far rather plan around it with you than find out afterwards that doses were missed.

Extra care is worth taking, particularly on the days when your white cell count is at its lowest. Food that is freshly cooked and served hot carries less risk than food that has been sitting out, and that is the main principle to work from. Street food, cut fruit from a stall, unpasteurised milk products and anything reheated repeatedly are the usual things teams suggest avoiding during those days. This is not a permanent restriction — it applies most to the low-count window in each cycle. Ask your team when yours falls.

Ask before you start any of them. Protein supplements are sometimes recommended when someone cannot get enough from food, and in that situation they are useful. Herbal preparations, high-dose vitamins and immunity boosters are a different matter: some interact with chemotherapy drugs or affect how the liver processes them, and your oncologist cannot account for what they do not know you are taking. Bring the actual packet to your appointment. That is the quickest way to get a clear answer on whether it is safe to continue.