What should you know about keto and glioblastoma?

A ketogenic diet is high in fat and low in carbohydrate. Interest in it comes from the way cells use energy, but dietary changes do not remove a brain tumour or replace surgery, radiotherapy, or medicines. Glioblastoma care is planned around the tumour's position, symptoms, scans, tissue findings, and overall health.

A restrictive diet can make it harder to maintain weight, strength, hydration, and medication tolerance. It may also interact with diabetes treatment or other medical conditions. A dietitian can check whether a proposed plan supplies enough energy and protein and can adapt it when appetite, swallowing, nausea, or fatigue changes.

Tell the neuro-oncology team about supplements, fasting, or a planned ketogenic diet before starting it. Keep prescribed treatment appointments and ask whether a diet change could affect blood glucose, bowel habits, hydration, or the timing of medicines. Prioritise manageable meals and fluids when treatment or symptoms reduce appetite.

Ask whether a dietitian with oncology experience can create a safe plan. Depending on the treatment pathway, the team may discuss brain tumour surgery, radiotherapy, chemotherapy, symptom medicines, rehabilitation, or a clinical trial. Dietary advice should support these decisions rather than delay them.

Seek urgent medical help for a new seizure, sudden weakness, trouble speaking, severe confusion, repeated vomiting, a rapidly worsening headache, or reduced alertness. Contact the treatment team for persistent vomiting, inability to keep fluids down, marked drowsiness, or symptoms that change after a diet or supplement is introduced.

Could this diet be unsafe with my medicines or medical conditions? How will weight, hydration, glucose, and strength be monitored? What foods are realistic during treatment? Should I meet an oncology dietitian? Which symptoms should prompt an urgent call?