Having chemotherapy when you have diabetes

Yes. Diabetes is one of the most common health conditions in people starting chemotherapy in India, and it very rarely stops treatment. What it does mean is that blood sugar needs closer attention during treatment. Sugars often rise, sometimes sharply, and the main reason is usually not the chemotherapy itself but the steroid medicines given alongside it. Steroids such as dexamethasone are widely used to prevent sickness and allergic reactions, and they push blood sugar up for a day or more after each dose. People who already have diabetes, and even some who have never been diagnosed, can see readings far higher than usual. With planning, monitoring and timely changes to diabetes medicines by your doctors, most people with diabetes complete chemotherapy safely.

Other parts of treatment affect sugars too. Sickness, vomiting and poor appetite can make sugars fall if you take insulin or certain tablets but are eating much less. Infections raise sugars. Some cancer medicines, including some targeted and immunotherapy medicines, can affect blood sugar in their own ways. At the same time, diabetes can affect how well you cope with chemotherapy. High sugars slow healing, raise infection risk and can worsen nerve damage in the hands and feet, which some chemotherapy medicines also cause. Diabetes that affects the kidneys can change which chemotherapy medicines are suitable or how they are given. This is why your oncologist will want to know about your diabetes, its complications and all your medicines before treatment begins.

The key is teamwork. Your oncology team, your diabetes doctor or physician, and you all have a part to play. Your doctors decide on any changes to diabetes medicines; you and your family check sugars as advised and report readings and symptoms. Never start, stop or change a diabetes medicine on your own because of chemotherapy. Instead, ask before the first cycle who will adjust medicines and how to reach them when readings are high or low.

Steroids are the usual cause of high sugars

Tell your team you have diabetes before steroid medicines are given. Sometimes the steroid plan can be adapted.

Low sugars matter too

Eating less while on insulin or some tablets can cause dangerous lows. Report poor appetite.

HbA1c helps planning

A blood test showing average sugar control over recent months helps your team plan.

It cannot tell you how your diabetes medicines should change, or what sugar readings are right for you during treatment. Targets and adjustments depend on your type of diabetes, medicines, other conditions and the chemotherapy plan, and must come from your doctors.

It also cannot tell you which chemotherapy is suitable if diabetes has affected your kidneys, nerves or heart. Your oncologist will take these into account.

Type 1 and type 2 diabetes

People with type 1 diabetes always need insulin and can become unwell quickly if sugars rise or they stop eating. They need especially close contact with their diabetes team during treatment. People with type 2 diabetes managed by tablets alone may need insulin for a while during steroid treatment, which is common and usually temporary. Needing insulin during chemotherapy does not mean diabetes has become permanently worse.

Diabetes discovered during treatment

Some people are found to have diabetes for the first time when steroid medicines push their sugars up. Others develop high sugars only while taking steroids. Your team will check and advise whether this needs ongoing treatment after chemotherapy ends. Screening for diabetes before treatment helps avoid surprises.

Food during chemotherapy

Eating enough matters more than strict dieting during treatment. Small, regular meals with protein, vegetables and whole grains help. When appetite is poor, your team or a dietitian can advise how to balance nutrition and sugar control. Avoid long gaps without food if you take insulin or certain tablets.

Foot and skin care

Check your feet daily, especially if nerve damage reduces feeling. Report cuts, blisters or redness early, as infections heal slowly with high sugars and low white cells.

Family support

A family member who can help check sugars, keep a record and call the team is valuable, especially after treatment days when tiredness and sickness are worst.

Which diabetes medicines may need attention

Several common diabetes medicines need thought during chemotherapy. Doctors may pause metformin when there is vomiting, dehydration, kidney problems or before some contrast scans. Sulfonylurea tablets such as glimepiride or gliclazide can cause low sugars when appetite is poor. Tablets that make the kidneys pass sugar in urine, such as dapagliflozin or empagliflozin, may be reviewed during illness or dehydration because of a rare but serious acid build-up in the blood. Insulin plans may need changing when steroids are given. These are decisions for your doctors and vary between people, so bring an up-to-date list of every medicine you take.

Nerve damage and foot safety

Some chemotherapy medicines, such as paclitaxel, docetaxel, oxaliplatin and vincristine, can cause numbness or tingling in the hands and feet. People with diabetes who already have nerve damage may notice this sooner or more strongly. Tell your team about any existing numbness before treatment and report any change. Wear well-fitting footwear at home and outside, check feet daily and avoid walking barefoot.

Eyes, heart and kidneys

Diabetes can affect the eyes, heart and kidneys over time. Before chemotherapy, your team may check kidney function and heart health, as these influence treatment choices. Keep regular eye checks going if possible, and tell your team about any heart symptoms.

What to do next

Tell your oncologist about your diabetes and medicines, bring recent tests, agree who will adjust medicines, check sugars as advised and keep a record, never change diabetes medicines on your own, and seek urgent help for very high or low readings.