Summer heat affects blood sugar in ways many diabetic patients do not expect. Our diabetology team in Borivali explains what to watch for and how to stay safe in May.
May in Mumbai is brutal. Temperatures push past 35 degrees, humidity makes everything feel heavier, and the heat lingers well into the night. For most people, it means switching to lighter meals and drinking more water. For someone managing diabetes, it means all of that plus a set of specific challenges that do not get talked about nearly enough.
If you or someone in your family is diabetic, here is what May and the lead-up to the monsoon actually does to blood sugar, and how to stay on top of it.
When your body is hot, several things happen at the same time. You sweat more, which affects hydration. Blood vessels dilate, which changes circulation. And insulin, the hormone that moves glucose from your blood into your cells, can become less effective or more unpredictable in high temperatures.
For a person without diabetes, the body adjusts automatically. For someone with Type 1 or Type 2 diabetes, these variables stack up in ways that can cause blood sugar to swing unexpectedly. Sometimes high, sometimes low, and sometimes both within the same day.
1. Dehydration raises blood sugar
When you are dehydrated, your blood becomes more concentrated, including the glucose in it. This pushes blood sugar readings higher even if you have not eaten differently. In Mumbai's May heat, dehydration happens faster than most people realise, especially for older adults who may not feel thirsty until they are already behind on fluids.
2. Insulin absorption becomes unpredictable
For patients on insulin injections, heat causes blood vessels near the skin to dilate. This means insulin injected into areas like the thigh or abdomen may absorb faster than usual, leading to an unexpected drop in blood sugar that can feel like dizziness, weakness, or confusion.
3. Stored insulin loses effectiveness in heat
Insulin stored above 30 degrees Celsius can degrade and become less effective. If your insulin is stored somewhere that gets warm during the day - near a window or in a bag left in a car - it is worth reviewing how you are storing and transporting it.
4. Heat exhaustion and low blood sugar feel similar
This is genuinely dangerous. Heat exhaustion causes sweating, weakness, rapid heartbeat, and confusion. So does low blood sugar. A diabetic patient who is also heat-affected may not be able to tell which problem they are dealing with. Both the patient and their family members should know the difference and how to respond.
5. Foot complications worsen in summer
Walking on hot surfaces without noticing heat damage is a serious risk for diabetics who have peripheral neuropathy, a condition where nerve damage reduces sensation in the feet. Burns and blisters that a non-diabetic would feel immediately can go unnoticed for hours. In diabetic patients, these wounds are significantly harder to heal.
Check your blood sugar more frequently. During summer months, testing more often than usual, particularly if you notice unusual symptoms, gives you a clearer picture of how heat is affecting your readings. Do not assume your numbers are stable just because your diet has not changed.
Hydrate deliberately. Do not wait until you feel thirsty. Set a target of at least 2.5 to 3 litres of water per day, more if you are spending time outdoors. Avoid sweetened drinks, packaged juices, and energy drinks even if they are marketed as hydration products. Plain water, buttermilk, and diluted coconut water are better choices.
Time outdoor activity carefully. If you walk, exercise, or do any activity outdoors, avoid the hours between 11 AM and 4 PM when temperatures peak. Early morning or post-7 PM are significantly safer for both your core temperature and for maintaining stable blood sugar during activity.
Inspect your feet daily. Every evening, check the soles of your feet, between your toes, and your heels. You are looking for redness, blisters, cuts, or any areas that look different from the day before. If you find anything, see a doctor the same day rather than waiting. Our diabetology team at Aarogyam can assess and manage diabetic foot concerns promptly.
Review your medication with your doctor. If your readings have been less predictable this month, that is worth a conversation with your doctor and not an adjustment you should make on your own. Doses that worked well in February may need revisiting for summer conditions. Book an appointment with our diabetology team if your numbers have been harder to control recently.
The big summer dietary changes most diabetics know: eat lighter, avoid fried foods, cut back on refined carbohydrates. A few less obvious adjustments also make a real difference this time of year:
Eat smaller meals more frequently rather than two or three large ones. Large meals cause bigger glucose spikes, which are harder to manage when your body is already dealing with heat stress.
Include cooling foods that are naturally low-glycaemic: cucumber, bottle gourd (lauki), ridge gourd (tori), yoghurt, and leafy greens are all good additions to a summer diabetic diet.
Be cautious with mangoes and chikoo. These are peak-season summer fruits in Mumbai and both are beloved, but both carry a significant sugar load. One or two slices of mango as part of a meal is manageable for many Type 2 diabetics. A whole mango on an empty stomach is a different matter. Know your own readings and portion accordingly.
Watch the mithai and sherbet season. May weddings, summer gatherings, and festive occasions mean increased exposure to sweets and sweetened drinks. Plan for these occasions rather than improvising.
Go to a hospital immediately if you or a family member with diabetes experiences:
Blood sugar reading above 300 mg/dL that does not come down
Signs of severe low blood sugar: confusion, fainting, inability to swallow, seizure
A foot wound that has changed colour, has an odour, or shows any sign of discharge
Chest pain, breathlessness, or extreme fatigue alongside high blood sugar
Our emergency line at Aarogyam is 1800 0902, available 24 hours. For non-urgent concerns, our doctors are available for scheduled appointments including evening slots at our Borivali East clinic.
If you have not had your HbA1c checked in the last three months, May is a good time to do it. This single blood test gives a three-month average of your blood sugar control, far more meaningful than a single fasting reading. It tells both you and your doctor whether your overall management is on track or needs adjustment. Call us on +91 916 777 6600 to arrange this at our Borivali clinic.
Does heat directly raise blood sugar? Heat itself does not directly raise blood sugar, but it creates conditions that do. Dehydration concentrates glucose in the blood. Heat-induced stress raises cortisol, which can push blood sugar up. And heat affects how quickly insulin is absorbed and used. The combined effect is that blood sugar becomes harder to predict and control during Mumbai summers.
My blood sugar readings have been higher this month even though my diet has not changed. Should I adjust my medication? Do not adjust medication on your own. Higher summer readings are common and have several possible explanations. The right response is to speak with your doctor, who can review your full picture including readings, medication, activity level, and hydration, and advise accordingly. Call us on +91 916 777 6600 or book an appointment online.
Is it safe to exercise outdoors if I am diabetic? Yes, exercise is important and beneficial for diabetics. The summer caveat is timing and hydration. Avoid outdoor exercise between 11 AM and 4 PM. Carry water and a fast-acting carbohydrate source like glucose tablets or fruit juice if you are on insulin, in case blood sugar drops during activity. Check your blood sugar before and after exercise until you understand how your body responds.
Can diabetes affect how well my body cools itself? Yes. Diabetics with autonomic neuropathy, where nerve damage affects involuntary functions, may have impaired sweating, which is the body's primary cooling mechanism. This makes them more vulnerable to heat exhaustion and heat stroke. If you have been diabetic for many years, have poor sensation in your feet, or have had consistently high readings, discuss heat tolerance with your doctor.
Does Aarogyam Hospital have a diabetologist in Borivali? Yes. Our diabetology and endocrinology department at Aarogyam Multispeciality Hospital in Borivali East is available by appointment. We offer HbA1c testing, blood sugar monitoring, diet counselling through our dietetics team, and full management of both Type 1 and Type 2 diabetes. Book an appointment here or call +91 916 777 6600.
