High Blood Sugar in Stomach Cancer: What It Means and How to Manage It

High blood sugar (hyperglycemia) during stomach cancer care is fairly common and is worth paying attention to. It can be caused by pre‑existing diabetes, stress from illness, steroids used with chemotherapy to prevent nausea, and sometimes the cancer treatment itself. Keeping glucose in a reasonable range can lower infection risk and support safer treatment. ^[1] Managing blood sugar generally should not take a back seat during cancer therapy, because better control may reduce complications such as infections and hospitalizations. ^{[2] [3]}

Why blood sugar can rise during cancer care

• Steroid medicines often given with chemotherapy can raise blood glucose, sometimes significantly. ^[1]
• Some cancer therapies and supportive medications can worsen or unmask diabetes. ^[4]
• Illness stress, reduced activity, changes in eating, vomiting, or dehydration can all push sugars higher. ^[1]

Why it matters

• Higher glucose can increase the chance of infections, which may interrupt or delay chemotherapy or surgery. ^[2]
• Among people undergoing cancer care, having diabetes is associated with higher rates of hospital stays, suggesting more complications when glucose is uncontrolled. ^[3]
• Tighter diabetes control has been associated with better outcomes in some cancers, and careful management is encouraged to offset risks; while this evidence is strongest in liver cancer data, it supports the general principle that good glycemic control is protective. ^{[5] [6]}

Is this specific to stomach cancer?

There is limited stomach‑cancer–specific guidance on hyperglycemia, but the general oncology and diabetes principles still apply: avoid sustained high sugars to reduce infection and treatment interruptions. ^{[7] [8]} Keeping glucose within target ranges is considered part of good supportive care during chemotherapy. ^[9]

Practical glucose targets and safety

• Cancer programs commonly flag concerning glucose levels using standardized criteria and recommend proactive management when values exceed thresholds; persistent readings above about 200 mg/dL often warrant medication adjustments during treatment. ^[9]
• Very high glucose accompanied by symptoms like excessive thirst, frequent urination, vomiting, or confusion needs urgent medical review to rule out emergencies. ^[9]

What you can do now

• Keep monitoring: Track fasting and pre‑meal glucose when possible, and check extra on chemotherapy days if you receive steroids. ^[9]
• Share readings: Let your oncology and primary care/diabetes teams see your weekly glucose trends so they can adjust plans early. Coordinated care helps prevent avoidable hospital visits. ^[10]
• Medication adjustments: It’s common to need temporary changes such as short‑term insulin or dose increases during steroid use or active chemo to keep sugars in range. ^[9]
• Nutrition strategies: Aim for smaller, frequent meals with protein and fiber, and choose lower‑glycemic carbohydrates; this supports glucose control even if appetite is variable during treatment. Managing sugars can help lower infection risk while on therapy. ^[2]
• Illness rules: If vomiting or unable to eat, check glucose more often and contact your team early for guidance to avoid dehydration and severe highs. ^[9]

When to be concerned

• Repeated glucose readings above 200 mg/dL, especially with symptoms or on days without steroids. ^[9]
• Signs of infection (fever, chills, new cough, painful urination) because high glucose can make infections more likely and harder to control. ^[2]
• Any sudden change in mental status, severe fatigue, or dehydration, which can signal a glucose emergency. ^[9]

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Quick reference: causes, risks, and actions

Topic	What to know	Why it matters	What to do
Steroid-related spikes	Common with chemo anti-nausea regimens	Can push glucose >200 mg/dL	Plan temporary med adjustments on steroid days
Infection risk	High glucose weakens immune defenses	Can delay treatment, increase hospital stays	Keep glucose in target, report fevers early
Coordinated care	Diabetes often gets deprioritized during cancer	Missed management leads to worse outcomes	Share logs with oncology and primary care
Nutrition during chemo	Appetite changes and vomiting affect glucose	Swings in intake drive highs/lows	Small, balanced, lower‑glycemic meals
Warning thresholds	Persistent >200 mg/dL needs attention	Prevent emergencies and interruptions	Call team for medication adjustments

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Bottom line

High blood sugar during stomach cancer care is common and manageable. Keeping glucose within reasonable targets can help lower infection risk, reduce hospitalizations, and keep treatment on schedule. ^{[2] [3]} Working proactively with your care team especially around steroid days and chemotherapy cycles can make a meaningful difference. ^{[1] [9] [10]}