high sugar MRI what to expect
Informed by recognized medical guidance
Overview
An MRI (magnetic resonance imaging) is a safe scan that uses magnets and radio waves to create detailed pictures of the inside of your body. Having high blood sugar (a high level of glucose in your blood) can affect how you feel and, in some cases, may influence how the MRI team prepares you for the scan. This article explains what to expect if you have high blood sugar and need an MRI.
Key facts
- MRI uses strong magnets and radio waves to make detailed images.
- High blood sugar can make you feel unwell, so let the MRI team know.
- You may need to check your blood sugar level before the scan.
- Follow the fasting or eating instructions given by the MRI department.
Yes. Many people who need an MRI have diabetes or periods of high blood sugar. MRI departments are used to helping these patients get safely scanned.
It can affect anyone with diabetes (type 1 or type 2), as well as people with temporary high blood sugar from stress, infection, or certain medicines.
Symptoms
- Very high blood sugar readings (above the level your doctor told you about)
- Vomiting and inability to keep fluids down
- Breath that smells fruity or sweet
- Difficulty breathing
- Confusion or unconsciousness
- ⚠Fever with high blood sugar
- ⚠Blood sugar that stays very high after taking your usual medicine
- ⚠Signs of dehydration (dark urine, dry lips, sunken eyes)
- ⚠You feel too unwell to manage at home
Common symptoms
- Increased thirst
- Passing urine more often than usual
- Feeling tired or weak
- Blurred vision
- Headache
Symptoms in children
- Bedwetting (if older child)
- Losing weight for no obvious reason
- Unusually cranky or tired
Symptoms in older adults
- Confusion or feeling 'foggy'
- Dizziness
- Dry mouth
- Increased thirst or urination, though sometimes less obvious
Causes
Main causes
- Diabetes (type 1 or type 2) that is not well controlled
- Not taking your usual diabetes medicines correctly
- Eating more carbohydrate than usual
- Infection or other illness
- Stress or strong emotions
- Certain medicines such as steroids (always talk to your doctor about this)
Risk factors
- Living with diabetes
- Having a recent infection or surgery
- Being less active than usual
- Having a cold, flu, or other acute illness
When to see a doctor
See a doctor urgently if:
- If your blood sugar is persistently high and you feel unwell
- If you cannot control your blood sugar with your usual routine
Book a routine appointment if:
- If you have symptoms of high blood sugar more than once or twice
- Before any MRI, tell the radiology department about your diabetes and your most recent blood sugar results
Diagnosis
High blood sugar is usually diagnosed with a simple finger-prick test that gives a glucose number. You may already have a glucose meter at home.
Tests that may be done
- Finger-prick blood glucose test
- Blood test from a vein (fasting glucose or HbA1c)
- Urine test for ketones (if your sugar is very high)
What to expect at your appointment
Before your MRI, the MRI department may ask you to check your blood sugar and tell them the result. If it's very high, they may ask you to wait until it comes down, or they may advise you to speak with your diabetes team. You'll also be asked about any medicines you take, and whether you need to fast. Most MRI scans do not require fasting, but some scans (especially with a contrast injection) may have specific instructions.
Treatment
The treatment for high blood sugar around the time of your MRI is to safely bring your glucose down to a more normal level. This might mean taking your usual diabetes medicine (as prescribed), eating a balanced snack, or following your doctor's advice. The MRI team will not give you new diabetes medication, but they will coordinate with you and your healthcare team.
Self-care at home
- Tell the MRI team you have diabetes or high blood sugar before the day.
- Ask whether you should take your usual morning medicine on the day of the scan.
- Bring your glucose meter, test strips, and a fast-acting source of glucose (like small sweets or juice) in case your sugar drops.
- Follow any fasting instructions exactly – if you're told to fast, ask when to take your medicine.
Medical treatments
If your blood sugar is very high, your doctor or diabetes nurse may adjust your usual diabetes medication or temporarily use an insulin shot. This is always based on your individual needs and doctor's advice. Never stop or start any diabetes medicine without talking to your healthcare provider.
When is surgery considered?
If you are having MRI-guided surgery, your blood sugar may be checked before the procedure and again before the scan. This is routine.
Living with this condition
If you have diabetes, check your blood sugar regularly and keep a record. This helps you and your healthcare team see patterns and adjust your plan.
Lifestyle tips
- Eat balanced meals with a steady amount of carbohydrate.
- Try to be physically active most days of the week.
- Get enough sleep to help with blood sugar control.
- Limit sugary drinks and highly processed foods.
Diet and exercise
Eating regular meals and staying active helps keep your blood sugar steadier. Work with a dietitian or diabetes educator to create a plan that suits you. Even a short walk after meals can help lower blood sugar.
Mental health and emotional wellbeing
Living with high blood sugar can feel stressful and worrying, especially before a medical scan. It's normal to feel anxious. Talk to your healthcare team about your worries, and remember that the MRI staff are there to help you.
Prevention
High blood sugar can sometimes be prevented with a healthy lifestyle, such as eating well, staying active, and keeping a healthy weight. If you already have diabetes, following your care plan can help prevent sudden spikes.
Vaccines
Be sure to stay up to date on your vaccinations, including the flu and pneumonia vaccines, because infections can cause blood sugar to rise. Ask your pharmacist or doctor about what's recommended for you.
Screening programmes
If you have risk factors for diabetes, ask your doctor about a simple blood test to check your blood sugar. Screening helps catch problems early.
Complications
If left untreated
- When high blood sugar is very high and left without treatment, it can lead to dehydration, a serious condition called diabetic ketoacidosis (DKA), or a very high glucose state called hyperosmolar hyperglycemic state. These can be life-threatening and require emergency care.
Long-term outlook
For most people, an MRI with high blood sugar can be completed safely. By working closely with your healthcare team and keeping track of your blood sugar, you can reduce risks and keep your health on track. Many people with diabetes live full, active lives and have scans without problems.
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
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Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 31, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.