How to Train Someone With Diabetes for Safe Exercise: Blood Sugar Levels, Intensities & Contraindications
Exercise can be one of the most useful tools for managing diabetes, but it also changes blood glucose quickly. A session that feels routine for one person can cause hypoglycaemia in another, especially when insulin, food timing, heat, stress, or medication changes are involved.
Training someone with diabetes is not about treating them as fragile humans,. it is about planning well, checking the right things, and knowing when to pause.
This guide is for informational use only. Diabetes care should be individualised, and anyone with diabetes should follow advice from their GP, diabetes nurse, endocrinologist, or registered dietitian, especially if they use insulin, have complications, or are starting a new exercise programme.
Start with a diabetes safety screen
Before programming sets, reps, intervals, or mileage, gather basic information. This should be done respectfully and privately.
Key questions include:
What type of diabetes do they have?
Do they use insulin or medications that can cause hypoglycaemia?
Do they use a continuous glucose monitor, finger-prick testing, or both?
Have they had recent hypos, severe hypos, or reduced hypo awareness?
Do they have complications affecting eyes, kidneys, nerves, heart, or feet?
What do they usually eat before training?
What symptoms tell them their glucose is going low or high?
What has their clinical team advised about exercise?
A person with type 1 diabetes usually needs more detailed glucose planning because insulin is always part of treatment. Many people with type 2 diabetes can exercise safely with simple precautions, but some medicines raise the risk of low glucose.
The safest approach is to agree on a plan before the first hard session. This includes where glucose tablets are kept, when testing will happen, and what numbers mean “train”, “modify”, or “stop”.
Know the blood glucose ranges before exercise
Blood glucose is measured in mmol/L in the UK. The ranges below are general exercise guidelines, not personal medical targets.
Blood glucose before exercise | What it usually means | Practical training decision |
Below 4.0 mmol/L | Hypoglycaemia | Do not start. Treat with fast-acting carbohydrate and recheck. |
4.0 to 4.9 mmol/L | Low or near low | Take fast-acting carbohydrate before starting. Begin only once stable. |
5.0 to 6.9 mmol/L | Often safe, but may fall during aerobic work | Consider carbohydrate if using insulin or sulfonylureas, especially for moderate or long sessions. |
7.0 to 10.0 mmol/L | Common safe starting range | Usually suitable for most planned exercise. Monitor during longer sessions. |
10.1 to 13.9 mmol/L | Higher than ideal but often workable | Exercise may proceed if the person feels well. Monitor response. |
13.9 to 16.7 mmol/L | High glucose | Check ketones if type 1 diabetes or prone to ketosis. Avoid hard intervals if glucose is rising. |
Above 16.7 mmol/L | Very high glucose | Postpone if ketones are present, the person feels unwell, or glucose is rising. Seek clinical advice if persistent. |
For people with type 1 diabetes, ketones matter. Exercising with high glucose and ketones can worsen ketosis and increase risk of diabetic ketoacidosis. If blood or urine ketones are moderate to high, training should stop before it starts.
Aerobic exercise, such as brisk walking, cycling, swimming, or steady rowing, often lowers glucose. Short, intense exercise can raise glucose for some people because adrenaline prompts the liver to release glucose. That is why a high reading before a sprint session needs more caution than the same reading before a gentle walk.
Check glucose during and after training
A good session does not end when the last set is done. Blood glucose can fall after exercise, sometimes hours later. This is common after longer aerobic sessions, mixed circuits, or training later in the day.
Useful checking points include:
Before exercise
Every 30 minutes during longer sessions
Immediately after exercise
Two to four hours later if the session was hard or long
Before bed after evening training, especially for insulin users
Post-exercise readings need context.
Blood glucose after exercise | What to do |
Below 4.0 mmol/L | Treat as hypoglycaemia with fast-acting carbohydrate. Recheck after 10 to 15 minutes. |
4.0 to 5.5 mmol/L | Eat carbohydrate if more activity is planned or the person is at risk of delayed hypo. |
5.6 to 10.0 mmol/L | Often a reasonable recovery range. Continue normal monitoring. |
Above 10.0 mmol/L | Recheck later. Look at hydration, intensity, stress, missed medication, or food timing. |
Above 13.9 mmol/L | Consider ketone testing in type 1 diabetes or if unwell. Avoid extra hard exercise until stable. |
The usual treatment for a hypo is 15 to 20 g of fast-acting carbohydrate, such as glucose tablets, glucose gel, or a sugary drink. Recheck and repeat if needed. Chocolate is less reliable for fast treatment because fat slows absorption.
If the person becomes confused, drowsy, unable to swallow, or loses consciousness, this is an emergency. Do not give food or drink by mouth. Use glucagon if available and trained to do so, and call emergency services.
Match exercise intensity to risk
Training intensity affects glucose response. So does duration, temperature, previous food intake, insulin on board, stress, sleep, and fitness level.
Use the talk test and rating of perceived exertion, also called RPE, because heart rate can be affected by medication, autonomic neuropathy, caffeine, and fitness level.
Intensity | Talk test | RPE out of 10 | Common glucose effect |
Light | Can speak easily | 2 to 3 | Small fall or little change |
Moderate | Can speak in short sentences | 4 to 6 | Often lowers glucose gradually |
Vigorous | Only a few words at a time | 7 to 8 | May lower glucose later or raise it during the session |
Near maximal | Very difficult to speak | 9 to 10 | Can raise glucose during exercise and increase delayed hypo risk |
For most beginners, start with light to moderate aerobic exercise. A practical first target might be 10 to 20 minutes of brisk walking, cycling, or low-impact cardio, then build duration slowly.
Resistance training is also useful. It supports muscle mass, strength, insulin sensitivity, balance, and confidence. Start with controlled movements, good technique, and moderate loads.
A sensible resistance session might include:
Squat or sit-to-stand pattern
Hip hinge or glute bridge
Row or pulldown
Chest press or incline press-up
Step-up or split squat variation
Loaded carry or core stability exercise
For general training, use 1 to 3 sets of 8 to 15 repetitions at a controlled effort. Avoid breath-holding. Teach steady breathing, especially for anyone with blood pressure, eye, or cardiovascular concerns (co-morbidities of diabetes).
High-intensity interval training can work well for some people, but it should not be the starting point for someone with unstable glucose, poor hypo awareness, untreated complications, or low fitness. Build a base first and progress slowly!
Know the main contraindications to exercise
Some situations call for stopping, modifying, or postponing exercise.
Do not train, or stop the session, if any of the following occur:
Blood glucose is below 4.0 mmol/L
Symptoms of hypoglycaemia appear
High glucose is present with ketones
The person feels acutely unwell, feverish, nauseous, or dehydrated
Chest pain, unusual breathlessness, faintness, or severe dizziness occurs
New neurological symptoms appear, such as weakness, confusion, or slurred speech
There is an active foot ulcer, infected blister, or open wound
Vision changes, sudden severe headache, or eye pain occur
Blood pressure is dangerously high, if known
The person has been medically advised to avoid exercise
Diabetes complications do not always rule out exercise, but they change the plan.
Peripheral neuropathy can reduce feeling in the feet. This raises the risk of blisters, pressure sores, and unnoticed injury. Choose well-fitting shoes, inspect feet, avoid repetitive high-impact work if sensation is poor, and consider cycling, swimming, rowing, or supported strength work.
Autonomic neuropathy can affect heart rate, blood pressure, digestion, and heat tolerance. Warm-ups, cool-downs, hydration, and conservative intensity choices become more important.
Retinopathy may require avoiding heavy lifting, maximal effort, breath-holding, high-impact work, and positions where the head is below the heart. This is especially relevant in proliferative retinopathy or recent eye treatment.
Kidney disease may affect blood pressure, fatigue, anaemia, and exercise tolerance. Training can still be valuable, but intensity should be agreed with the clinical team.
Cardiovascular disease risk is higher in diabetes. Someone with chest pain, known heart disease, unexplained breathlessness, or long-term sedentary behaviour may need medical clearance before vigorous exercise.
Medications
The medications diabetics are on have many effects and side effects. For this reason we won't discuss them in detail here. If you wish to learn more about this subject, please book onto our Long-term Health Conditions qualification.
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