How to Increase Glucose in Blood Safely

Knowing how to increase glucose in blood quickly and safely is essential for anyone managing hypoglycaemia, whether caused by diabetes medication, missed meals or intense exercise. When blood glucose falls below 4 mmol/L, the brain is among the first organs affected, and symptoms can escalate rapidly. This article explains why blood glucose drops, how to raise it effectively using fast-acting carbohydrates, which foods and drinks are most suitable, when to seek urgent medical help, and how to prevent future episodes, all in line with NHS, NICE and Diabetes UK guidance.

Why does blood glucose drop and what causes it?

Blood glucose drops below 4 mmol/L most commonly due to diabetes medication such as insulin or sulfonylureas, particularly if a meal is skipped or exercise is more intense than usual. Alcohol, prolonged fasting and certain medical conditions can also cause hypoglycaemia.

Blood glucose drops, a condition known as hypoglycaemia, when the level of glucose in the bloodstream falls below approximately 4 mmol/L. This threshold is used in NHS and Diabetes UK guidance as the point at which treatment is needed. Glucose is the body's primary fuel source, and the brain is particularly sensitive to any shortfall, which is why symptoms can appear quickly and feel alarming.

The most common cause is diabetes medication, particularly insulin and sulfonylureas such as gliclazide, which lower blood glucose as part of their mechanism of action.^[2][16] If a dose is too high, a meal is skipped or delayed, or physical activity is more intense than usual, the medication can push glucose lower than intended. People without diabetes can also experience hypoglycaemia, though this is less common; recurrent episodes in someone without diabetes warrant assessment for underlying causes such as insulinoma, liver disease or endocrine conditions, and should be investigated through a GP.

Other contributing factors include:

• Excessive alcohol consumption, especially on an empty stomach, which impairs the liver's ability to release stored glucose

• Prolonged or intense exercise that depletes glycogen stores faster than they are replenished

• Certain medical conditions, including Addison's disease, liver disease or insulinoma (a rare insulin-secreting tumour)

• Irregular eating patterns, such as very low-calorie diets or extended fasting

It is also worth noting that some medicines, including beta-blockers, and complications such as autonomic neuropathy can blunt the warning symptoms of hypoglycaemia (a condition called hypoglycaemia unawareness), making it harder to recognise a falling glucose level in time to treat it.^[12][13] Anyone who suspects they may have hypoglycaemia unawareness should discuss this promptly with their GP or diabetes team.

Understanding the underlying cause is important because it shapes both the immediate treatment and longer-term prevention. Anyone experiencing recurrent episodes of low blood glucose should discuss this with their GP, as it may indicate that a medication dose needs reviewing or that further investigation is warranted.

How can you raise your blood sugar quickly and safely?

Consume 15 to 20 grams of fast-acting carbohydrate such as glucose tablets, fruit juice or a sugary drink, then recheck blood glucose after 15 minutes and repeat if still below 4 mmol/L. Follow with a slower-releasing carbohydrate snack if your next meal is more than one hour away.

The fastest and safest way to raise blood glucose during a hypoglycaemic episode is to consume 15 to 20 grams of fast-acting carbohydrate as soon as symptoms are recognised. This stepwise approach is recommended by NHS and Diabetes UK guidance for people with diabetes who are conscious and able to swallow safely.

Examples of suitable fast-acting carbohydrate sources providing approximately 15 to 20 grams include:

• 5 to 7 glucose or dextrose tablets (check the pack for the exact carbohydrate content per tablet, as this varies by brand)

• 150 to 200 ml of a sugary (non-diet) fizzy drink such as full-sugar cola or lemonade

• A small glass (150 to 200 ml) of fruit juice

• 4 to 5 jelly babies or similar glucose-containing sweets (check the label, as carbohydrate content varies)

• A glucose gel sachet, which can be placed inside the cheek and absorbed through the mouth lining in conscious patients who have difficulty swallowing; do not give anything by mouth if the person is drowsy or unconscious

If you are taking acarbose (a medicine that slows carbohydrate digestion), sucrose-containing options such as ordinary sweets or table sugar are less effective at raising blood glucose quickly. In this case, use glucose or dextrose tablets, gel or a glucose drink specifically, as these bypass the effect of acarbose.

After consuming the fast-acting carbohydrate, wait 15 minutes and recheck blood glucose using a glucometer. If the level remains below 4 mmol/L, repeat the same amount of fast-acting carbohydrate. Once glucose has returned to a safe level (4 mmol/L or above), eat a small snack containing slower-releasing carbohydrate, such as a plain biscuit, a slice of bread or a small bowl of cereal, if your next meal is more than about one hour away or if you are taking a sulfonylurea or insulin (which continue to act and can cause a further dip). If your next meal is imminent, the snack may not be necessary, but follow your individual care plan if you have one.

Avoid the temptation to over-treat hypoglycaemia by consuming large quantities of sugary food, as this can cause a rebound rise in blood glucose (sometimes called reactive hyperglycaemia), which brings its own risks. Measured, stepwise treatment is both safer and more effective.

For children experiencing hypoglycaemia, carbohydrate amounts and the steps to follow should be guided by the child's diabetes team's written care plan, as doses differ from adult recommendations.

Which foods and drinks help restore normal glucose levels?

Full-sugar fizzy drinks, pure fruit juice and glucose tablets are the fastest-acting options for treating an active hypo due to their high glycaemic index. Chocolate and high-fat foods are not ideal first choices as fat slows glucose absorption.

Glucose tablets and sugary drinks are the most reliable first-line options for treating hypoglycaemia because they are absorbed rapidly into the bloodstream, but a range of everyday foods and drinks can also be effective when these are not available. The key characteristic to look for is a high glycaemic index (GI), meaning the carbohydrate is digested and absorbed quickly.

Fast-acting options (for treating an active hypo):

• Full-sugar fizzy drinks (not diet or sugar-free versions, which contain no glucose; always check the label)

• Pure fruit juice (orange, apple or grape)

• Glucose or dextrose tablets (check the pack for grams of carbohydrate per tablet)

• Honey or sugar dissolved in water

• Sweets such as jelly babies, wine gums or fruit pastilles (check the label for carbohydrate content, as amounts vary by brand)

If you take acarbose, choose glucose or dextrose tablets, gel or a glucose drink rather than sucrose-containing sweets or sugar, as acarbose reduces the effectiveness of sucrose at raising blood glucose quickly.

Slower-releasing foods (for stabilising glucose after treatment):

• Wholegrain bread or crackers with a protein-containing topping such as peanut butter or cheese

• Porridge oats or a small bowl of cereal

• A banana or other piece of fruit alongside a handful of nuts

• A glass of semi-skimmed milk, which provides both carbohydrate and protein

It is worth noting that foods high in fat, such as chocolate or crisps, are not ideal for treating hypoglycaemia despite containing sugar. Fat slows gastric emptying and therefore delays glucose absorption, meaning blood glucose rises more slowly than needed during an acute episode. Chocolate can be used as part of a follow-up stabilising snack once the immediate hypo has been treated, but it should not be the first choice.

People managing diabetes should keep a supply of fast-acting glucose (such as glucose tablets or a small carton of juice) with them at all times, particularly when driving, exercising or travelling.

When should you seek urgent medical help for low blood sugar?

Call 999 immediately if the person loses consciousness, has a seizure or cannot be roused, as these are medical emergencies. Contact NHS 111 or a GP if symptoms do not improve after two rounds of treatment or if hypoglycaemia is occurring frequently.

You should call 999 immediately if a person with hypoglycaemia loses consciousness, has a seizure, or cannot be roused, as these are medical emergencies requiring prompt intervention. In these situations, do not attempt to give food or drink by mouth, as there is a serious risk of choking.

If a glucagon emergency kit is available and the person administering it has been trained in its use, it can be given while waiting for the ambulance. Glucagon works by stimulating the liver to release stored glucose, raising blood glucose levels within 10 to 15 minutes.^[3] It is available on prescription for people at risk of severe hypoglycaemia. Household members and carers should be trained in how to use the kit and should check the expiry date regularly so it is ready when needed.

Contact NHS 111 or speak to a GP if:

• Symptoms do not improve after two rounds of fast-acting carbohydrate treatment (approximately 30 minutes)

• Hypoglycaemia is occurring frequently without a clear explanation

• You are unsure whether your current medication dose is appropriate

• A child experiences hypoglycaemia and you are uncertain how to manage it

• You suspect hypoglycaemia unawareness, meaning you are not getting the usual warning symptoms before your glucose drops dangerously low

Suspected side effects from diabetes medicines, including hypoglycaemia that appears to be medication-related, can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

People who drive must be aware of DVLA guidance on hypoglycaemia and diabetes. The DVLA advises checking blood glucose before driving and not driving if glucose is below 5 mmol/L. After treating a hypo, the DVLA advises waiting at least 45 minutes after blood glucose has recovered before resuming driving, because cognitive function can remain impaired even after glucose levels normalise. A severe hypo while driving can have serious consequences for road safety. The DVLA requires notification of certain diabetes-related conditions, and stricter standards apply to Group 2 licence holders (bus and lorry drivers).^[4] Full guidance is available on the GOV.UK DVLA diabetes and driving page.

How to prevent blood glucose from dropping too low again

Preventing recurrent hypoglycaemia involves regular medication review with a GP or diabetes team, eating at consistent times and monitoring blood glucose before driving or exercise. NICE guidance supports continuous glucose monitoring for people with type 1 diabetes or frequent hypoglycaemia.

Preventing recurrent hypoglycaemia involves identifying and addressing the specific triggers that caused the episode in the first place, which is best done in partnership with a GP, diabetes specialist nurse or pharmacist. Regular review of medication doses, particularly insulin or sulfonylureas, is one of the most effective preventive measures available.

Frequent or severe hypoglycaemic episodes, or suspected hypoglycaemia unawareness, should prompt an urgent review with the diabetes team, as these situations may require changes to medication, monitoring technology or both.

Practical steps that can help reduce the risk of future episodes include:

• Eating regular meals and snacks at consistent times to maintain a steady supply of glucose throughout the day

• Adjusting carbohydrate intake around exercise, particularly for longer or more intense sessions, by consuming additional slow-release carbohydrate beforehand

• Monitoring blood glucose regularly, especially before driving, exercising or going to bed, using a glucometer or a continuous glucose monitor (CGM) if one has been prescribed

• Limiting alcohol, and always eating food alongside any alcoholic drinks to reduce the risk of delayed hypoglycaemia

• Carrying fast-acting glucose at all times so that treatment is immediately available if needed

• Wearing or carrying medical identification (such as a medical alert bracelet or card) so that bystanders and emergency services are aware of your condition

• Following a personalised hypo action plan agreed with your diabetes team, which sets out your individual targets and steps to take

For people with type 1 diabetes or those experiencing frequent hypoglycaemia despite optimised medication, NICE guidance (NG17 for type 1 diabetes in adults and NG28 for type 2 diabetes in adults) supports the use of continuous glucose monitoring and, in some cases, insulin pump therapy, both of which can significantly reduce hypoglycaemic episodes. Speak to your diabetes team about whether these options are appropriate for you.

Structured diabetes self-management education programmes available through the NHS, such as DAFNE (Dose Adjustment For Normal Eating) for type 1 diabetes and DESMOND for type 2 diabetes, can also build long-term confidence in recognising and managing blood glucose.

Online consultations for weight management and related metabolic conditions, including prescriber review, are offered by services such as Bolt Pharmacy, a GPhC-registered UK online pharmacy, where a prescriber may consider appropriate treatment options following a clinical assessment.

Scientific References

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8. Blood glucose management | Type 2 diabetes in adults (NG28).
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10. Structured education programme | Type 2 diabetes in adults (QS209, Quality statement 2).
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