Medical Oncologist
Blood sugar during treatment
Eating to Control High Blood Sugar — From Cancer Drugs
Some cancer drugs raise blood sugar in people who have never had diabetes before. That can be frightening to hear — but it is a recognised, manageable side effect, and what you eat at each meal genuinely makes a difference.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- Steroids are the common cause — Dexamethasone and prednisolone block insulin from working properly, which raises blood sugar even in people with no prior history of diabetes.
- It can happen to anyone on treatment — Many patients who develop raised blood sugar during cancer treatment have never been told their blood sugar was high before.
- Diet changes do help — Specific food swaps — many already part of South Indian cooking — can slow the rise in blood sugar after meals.
- Medication may still be needed — Some patients need a short course of tablets or insulin alongside diet changes. This is common and often temporary.
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Some cancer drugs, especially steroids, raise blood sugar whether or not you have had diabetes before. Eating smaller portions more often, choosing lower-glycaemic grains, and adding protein and fibre to each meal all help. Tell your team, because some patients need medication alongside diet changes — food alone may not be enough.
Why do cancer drugs raise your blood sugar?
Steroids — particularly dexamethasone and prednisolone, which are widely used during cancer treatment to manage side effects and support the body — are the most common cause. They reduce the effectiveness of insulin, so glucose builds up in the blood. This can happen even if your blood sugar has always been normal.
Some targeted therapy drugs, particularly certain mTOR inhibitors, can have a similar effect. Your team may check your blood sugar more regularly once you start treatment, and that monitoring is intentional.
This side effect is not a sign that your cancer is worsening. It is a recognised metabolic response to the medication, and it often improves once the steroid dose is reduced or stopped.
What can you change at each meal to help?
- Switch white rice to hand-pounded, red, or parboiled rice — or replace part of the meal with ragi, jowar, or bajra
- Eat smaller portions more often: four to five smaller meals spread through the day rather than two large ones
- Add protein at every meal — a bowl of dal, a cup of curd, an egg, or a small piece of fish or chicken
- Eat your vegetable sabzi before the rice or roti portion, to slow how quickly glucose rises
- Avoid maida-based foods: white bread, biscuits, naan, and parotta raise blood sugar quickly
- Cut packaged juices, cold drinks, and heavily sweetened chai — these cause a rapid spike
- If you take steroids in the morning, eat a balanced meal before the tablet rather than on an empty stomach
- Tell your team everything you are consuming, including traditional remedies and herbal supplements
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Do you have to stop eating rice and roti completely?
You do not have to stop eating rice or roti. The portion size and what you eat alongside them matters more than whether you eat them at all.
A smaller portion of hand-pounded or red rice, eaten with plenty of dal, a vegetable, and a protein, raises blood sugar more slowly than a large plate of white rice eaten alone. A multigrain or wheat roti with sabzi and curd is a reasonable choice for most people.
If you have been told to drink fruit juice or eat large quantities of fruit to cleanse the body or keep up your strength, please tell your team. Fruit juice — including freshly squeezed juice — concentrates natural sugars and removes fibre, so it raises blood sugar more quickly than the same fruit eaten whole. Whole fruit in moderate amounts is generally fine.
When should you tell your team that your blood sugar is high?
Tell your oncology team if you have been told your blood sugar is elevated, or if you notice unusual thirst, passing urine much more often than normal, blurred vision, or unexplained tiredness without a clear other cause.
Diet changes are one part of management, not the whole answer. Some patients need a short course of oral medication or insulin during treatment. This is common, and for many people it is temporary — blood sugar often returns toward normal once the steroid dose is tapered.
Do not reduce your steroid dose on your own to try to bring blood sugar down. The dose has been set for a clinical reason, and changing it without guidance can interfere with your treatment.
Did you know?
Ragi, jowar, and bajra were staple grains across Telangana and Andhra Pradesh long before polished white rice became the norm. They have a lower glycaemic index than white rice, meaning they raise blood sugar more slowly. For patients managing treatment-related high blood sugar, returning to these grains is a practical, evidence-supported step.
Source: ICMR and WHO nutritional guidance on millets and glycaemic management in South Asian diets
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Common questions
Frequently asked questions
Is the high blood sugar from steroids the same as diabetes?
It is not the same condition, though the mechanism overlaps. Steroids make insulin less effective, which raises blood sugar in a way that is distinct from how type 2 diabetes develops. The key practical difference is that blood sugar often returns toward your baseline once the steroid dose is tapered or stopped. Some patients need medication during treatment, but most do not carry a diabetes diagnosis after treatment ends. Your team will monitor it and tell you what to expect.
Can I still drink tea or filter coffee during treatment?
Plain tea or filter coffee with little or no added sugar is generally fine in moderation. The issue is the amount of sugar added — several spoons of sugar across multiple cups a day adds up considerably. If you find it difficult to drink tea without sugar, try reducing the amount gradually over a week or two rather than stopping abruptly. Small amounts of milk do not raise blood sugar as sharply as sugar does.
I was told to drink a lot of fresh juice to keep my strength up. Is that safe?
Whole fruit in moderate amounts provides useful nutrients and is generally fine. Fruit juice — including freshly squeezed juice — is different. Juicing removes the fibre and concentrates the natural sugars, so a glass of juice raises blood sugar more quickly than the same fruit eaten whole. If you are regularly drinking juice to maintain strength, let your dietitian or oncology team know so they can suggest alternatives that support your nutrition without the spike.
Someone recommended karela juice or methi seeds for blood sugar. Should I try them?
Karela and methi are traditional foods, and some research has looked at their effects on blood sugar. They are not harmful when eaten as food — karela as a vegetable, methi in cooking. The concern arises when they are taken in concentrated supplement or extract form alongside cancer drugs, because how they interact with specific medications is not well studied. Before using concentrated forms of anything, including herbal or Ayurvedic supplements, tell your oncology team what you are considering. That conversation protects you.
Will my blood sugar go back to normal once treatment ends?
In many cases, yes — particularly when the main cause was steroid medication that has since been reduced or stopped. Blood sugar often returns toward your baseline as the dose is tapered. This does not happen for everyone, and some patients find that blood sugar remains mildly elevated after treatment, which their general physician then manages. Your team will monitor it and advise you whether you need ongoing treatment or can simply watch it over time.