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Reactive Hypoglycaemia following Bariatric surgery v3

Date Issued: January 2022

Review date: January 2024

Ref: C-342 v3

PDF: Reactive Hypoglycaemia following Bariatric Surgery final December 2021 v3.pdf [pdf] 194KB

What is reactive hypoglycaemia?

After bariatric surgery a small number of people can experience low blood glucose (sugar) levels. A low blood glucose level is defined as less than 4 mmol/L.
As you lose weight your body can become more sensitive to the insulin produced in response to carbohydrate in the diet.
Reactive hypoglycaemia can occur 1 - 3 hours after eating a meal or snack.

What are the symptoms of reactive hypoglycaemia?

Shaking, light headedness, dizziness, confusion, sweating, hunger, anxiety, palpitations, weakness, tiredness, blurred vision, disorientation and in severe cases loss of consciousness.

How is it different to Dumping Syndrome?

The symptoms above will improve once you eat or drink something containing carbohydrate.

How is suspected hypoglycaemia investigated?

You may be given a blood glucose monitor and shown how to record your blood glucose levels when you experience hypo like symptoms. Keep a log of the episodes.

You may also be asked to keep a food diary to look at your eating habits in more detail. Make sure you record the types and amounts of food and drink you consume, the time you had them and any symptoms as they occur. You should keep a diary for a week and bring it with you to your next appointment.
In the majority of cases reactive hypoglycaemia can be effectively treated through dietary changes alone. However, if your symptoms don’t improve or worsen despite implementing the changes above then please let the Dietitian know as you may need further investigations.

What to do if you have a low blood glucose level

Hypoglycaemia can be serious if left untreated and can lead to loss of consciousness. Therefore, if you have symptoms of profuse sweating and dizziness or know your blood glucose levels are below 4 mmol/L with any of the symptoms above, it is important to bring your blood glucose levels back within the normal range (between 4 - 7mmol/L) as quickly as possible.

How to treat a low blood glucose level

Step 1.) You will need to take a form of fast acting carbohydrate such as;
2-3 Dextrose tablets OR 120 mls of orange juice (to provide 6 – 12g carbohydrate).

Step 2.) If you have a glucose monitor, you should check your blood glucose levels after 15 minutes to ensure that they are above 4 mmol/L. If they are still low, repeat step 1.

Step 3.) You will then need to follow this up with a small snack containing carbohydrate and protein such as; a couple of wholegrain crackers and cheese / ½ a piece of toast with peanut butter / pitta bread and hummus, a small bowl of whole grain cereal or your next meal if it is due. This will help to stabilize your blood glucose levels.

Dietary Modifications to Help Prevent Reactive Hypoglycaemia

Follow the eating techniques recommended after bariatric surgery (see eating techniques booklet)
• Eat and drink separately, leaving at least 30 – 60 minutes before and after eating.
• Eat slowly and chew food well.
• Practice the 20-20-20 rule.
• Eat little and often.
• Eat protein first.

Avoid sugary and sweet foods

Sugars and refined carbohydrates such as sugar, honey, jam, marmalade, sweets, chocolate, cakes, biscuits, milkshakes, ice cream, white bread, white rolls, white rice, sugar coated breakfast cereals, squash, fruit juice and smoothies can cause blood glucose levels to rise rapidly. This will initiate an insulin response which in turn causes blood glucose levels to fall. Therefore, it is advisable to avoid these types of food.

Choose low sugar products

High sugar: more than 22.5g of total sugars per 100g
Low sugar: 5g of total sugars or less per 100g.

Choose complex carbohydrates such as wholegrain / granary bread, wholegrain / basmati rice, whole wheat pasta, wholegrain crackers, oatcakes, whole wheat pitta bread, boiled potatoes, wholegrain cereals such as porridge oats, Weetabix®, Shredded Wheat® and plain puffed wheat.

Don’t skip meals or snacks

Eat three regular meals plus two healthy snacks every day. Aim to eat every 2 – 3 hours, leaving no longer than 4 hours between eating.

Suggested Meal Plan:

Breakfast: Whole/ Jumbo porridge oats with chopped nuts & seeds
Mid morning snack: 1 -2 x oatcakes with soft cheese / ham / chicken / peanut butter.
Lunch: Tinned fish / egg / ham/ chicken and salad.
Mid afternoon snack: Diet/plain yoghurt or a boiled egg.
Evening meal: Lean meat, fish or beans/lentils with new potatoes & vegetables/salad.
Evening snack: chopped peppers/ carrots/cucumber & hummus/salsa dip.

Include protein at each meal

Focus on filling your side plate with ½ protein, ¼ vegetables / salad and then ¼ carbohydrates.
Eat your protein first, followed by vegetables or salad and then carbohydrates last if you have capacity.
A lower carbohydrate diet may help control the symptoms of reactive hypogylgaemia.

Ensure snacks contain protein and carbohydrate

Eating protein and carbohydrate together can slow down the rate at which glucose is released into the blood.
Suitable snacks; matchbox size cheese and chopped carrot /cucumber / peppers / olives, handful of unsalted nuts and a diet / natural greek yogurt, a couple of slices of ham and cherry tomatoes or oatcakes and cream cheese.

Avoid Alcohol

Alcohol is best avoided if hypoglycaemia is suspected because alcohol can also lower blood glucose levels.

Reduce Caffeine

It may be advisable to limit drinks to no more than 2-3 cups of caffeinated tea, coffee, green tea or soft drinks a day. You could try decaffeinated beverages as an alternative to these.


If you experience symptoms of reactive hypoglycaemia your ability to drive may be impaired. Driving is not recommended until your suspected reactive hypoglycaemia is investigated, a diagnosis is made and appropriate treatment provided if necessary.

Who to contact

Claire Woods, Bariatric Nurse Specialist
Rachel Griffin, Bariatric Dietitian
Ciara Caleshu, Bariatric Dietitian
Direct line 01752 431724, this is an answer phone. Please leave a message and you will be called back as soon as the message is picked up.
Ideally email us at: plh-tr.DerrifordBariatrics@nhs.net
If your query is urgent, phone Derriford Hospital switchboard on 01752 202082 and ask them to bleep the Bariatric Nurse.


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