Few health questions feel as confusing as "what should my glucose be" — units differ between countries, target values shift through the day, and many figures only apply once you have been diagnosed with diabetes.

This article uses mmol/L (the UK standard unit) and draws on official guidance from the NHS, NICE, the British Heart Foundation (BHF) and Diabetes UK.

It systematically answers common questions such as "what should my glucose level be" and "what should be my blood glucose level", mapped to the time of day.

One technical detail before we begin: continuous glucose monitors (CGM) measure glucose in interstitial fluid below the skin, rather than blood directly.

The physiological lag from interstitial fluid to blood is around 5 to 10 minutes, and reported overall system delays in the literature range from 5 to 40 minutes [1].

We work through the day in turn — fasting, post-meal, bedtime — and then layer on age, pregnancy and diabetes type, so you finish with a clear picture of your numbers and when to act.

What Should My Blood Glucose Level Be? A Quick Answer

The most direct answer: per BHF guidance for the UK, healthy adults without diabetes typically run fasting glucose between 4.0 and 5.4 mmol/L, and stay under 7.8 mmol/L two hours after eating [2].

For people with diabetes, Diabetes.co.uk gives these routine references — 4 to 7 mmol/L before meals, 5 to 9 mmol/L 90 minutes after a meal in type 1 diabetes, and under 8.5 mmol/L after a meal in type 2 diabetes [3].

The UK uses mmol/L by default while US sources usually use mg/dL. The conversion factor is 18 (mg/dL = mmol/L × 18).

The table below sets out a quick "by time of day" reference for 7 core UK targets (your individual numbers are personalised by your clinical team).

Time Point	No Diabetes (Reference)	With Diabetes (Reference)	Source
Fasting / On Waking	4.0–5.4 mmol/L	4–7 mmol/L	BHF / Diabetes UK
Before Meals (other times)	—	4–7 mmol/L	Diabetes UK
2 Hours After Eating	< 7.8 mmol/L	T1 5–9 mmol/L / T2 < 8.5 mmol/L	BHF / Diabetes UK
Before Bed	—	Individualised	Set by clinical team
HbA1c	< 42 mmol/mol (< 6.0%)	≤ 48 mmol/mol (≤ 6.5%)	NICE NG28 / Diabetes.co.uk
Time in Range (3.9–10 mmol/L)	—	≥ 70%	ATTD 2019 Consensus
Hypoglycaemia Threshold	< 4.0 mmol/L	< 4.0 mmol/L	Diabetes UK

Pregnancy targets are stricter — see the dedicated section below. If you are comparing different CGM supplies and monitoring options, this table works as a quick at-a-glance reference.

What Level Should My Glucose Be First Thing In The Morning?

Many readers search for "what should my fasting glucose be in the morning" or "what should my glucose be when i wake up" — both are essentially the same question.

For adults without diabetes, BHF suggests a morning fasting glucose of between 4.0 and 5.4 mmol/L.

If your morning fasting glucose is consistently 7.0 mmol/L or above, the NHS treats this as one diagnostic threshold for type 2 diabetes. An HbA1c of 48 mmol/mol (6.5%) or above is also a diagnostic standard given by the NHS [4].

"Fasting" clinically means no caloric intake for at least 8 hours. For adults with type 1 diabetes, Diabetes UK recommends a waking glucose target of 5 to 7 mmol/L.

An elevated morning glucose often involves the dawn phenomenon. In type 1 diabetes, nightly spikes in growth hormone secretion are the leading mechanism behind morning highs.

In type 2 diabetes, fasting hyperglycaemia at dawn is attributed to a transient rise in hepatic glucose production combined with insufficient compensatory insulin secretion [5].

Practical tip: take your reading within 30 minutes of getting up, before eating. If your fasting glucose stays above 7 mmol/L for several days alongside excessive thirst, frequent urination or unexplained weight loss, book a review with your GP.

What Should My Blood Glucose Be 2 Hours After Eating?

"What should my glucose be 2 hours after eating" is one of the most common follow-up searches in the UK SERP.

For people without diabetes, two-hour post-meal glucose should stay below 7.8 mmol/L (per BHF).

People with type 1 diabetes typically aim for 5 to 9 mmol/L 90 minutes after a meal, while those with type 2 diabetes aim for under 8.5 mmol/L (per Diabetes.co.uk).

Timing — start counting 2 hours from your first bite. Factors that influence post-meal peaks include the glycaemic index (GI) and load (GL) of the food, how quickly you eat, your current stress level and recent physical activity.

A randomised crossover study published in PMC found that a 30-minute brisk walk starting roughly 15 minutes after a meal substantially reduced the post-meal glucose peak, with the effect holding across meals of differing carbohydrate content and macronutrient composition [6].

In CGM user communities, many readers report that adding a "10 to 15 minute walk after meals" to their routine smooths their post-meal curves noticeably.

When comparing the trend arrows of different CGM brands, this pattern shows up consistently.

What Should My Glucose Be Before Bed?

Bedtime glucose — the search "what should my glucose be before bed" — is one of the most overlooked nodes in diabetes management, yet it is closely tied to overnight safety.

UK patient-facing pages from Diabetes UK and Diabetes.co.uk do not publish a fixed mmol/L bedtime target. Your specific bedtime number is set individually by your clinical team based on your insulin regimen and hypoglycaemia risk.

The general principle is to avoid going to sleep too low (because of nocturnal hypoglycaemia risk) or too high (because the elevation may carry into the morning). Discuss your personal cut-offs with your diabetes team.

Practically, take a reading within 30 minutes of bedtime. If you have done a high-intensity workout that day or eaten a late dinner, watch the overnight trend particularly closely.

Wearable devices from CGM suppliers commonly include "nocturnal hypoglycaemia alarms".

Alarm thresholds, default delays and customisability vary considerably by brand — refer to each brand's documentation.

What Should My Average Blood Glucose Be? HbA1c And Time In Range

"What should my average blood glucose be" actually points to two parallel metrics — HbA1c and Time in Range (TIR).

HbA1c reflects average glucose over the past 2 to 3 months. Diabetes.co.uk lists UK thresholds as normal < 42 mmol/mol (< 6.0%), prediabetes 42–47 mmol/mol (6.0–6.4%), and diabetes ≥ 48 mmol/mol (≥ 6.5%) [7].

NICE NG28 sets a routine adult type 2 diabetes management target of 48 mmol/mol or below. For people on medication that can cause hypoglycaemia, the target may be relaxed to 53 mmol/mol or below (per NICE NG28 public summary).

Time in Range (TIR) is the complementary metric of the CGM era. The 2019 international consensus published in Diabetes Care recommends that adults with type 1 or type 2 diabetes aim for a TIR (3.9 to 10.0 mmol/L) above 70% [8].

That benchmark works out to roughly 16 hours 48 minutes per day inside the target range.

TIR is usually only reliable to estimate via CGM, since finger-prick testing rarely covers a full day at five-minute resolution.

Note that HbA1c can be skewed in anaemia or haemoglobinopathies, so clinical teams interpret it alongside other indicators.

What Should My Glucose Numbers Be By Age, Pregnancy, And Diabetes Type?

The answer to "what should my glucose numbers be" varies considerably by age, diabetes type and pregnancy status.

Children with type 1 diabetes — per Diabetes UK, the reference range is 4 to 7 mmol/L when you wake up and before meals, and 5 to 9 mmol/L after meals.

Adults with type 1 diabetes — per Diabetes UK, 5 to 7 mmol/L when you wake up and before meals, 4 to 7 mmol/L before meals at other times of the day, and 5 to 9 mmol/L at least 90 minutes after eating.

Adults with type 2 diabetes — NICE NG28 gives HbA1c targets of 48 mmol/mol (or 53 mmol/mol if on medication that can cause hypoglycaemia), as already cited in the HbA1c section above, with targets agreed individually with the clinical team.

Routine pre/post-meal home meter targets in type 2 diabetes are individualised. Per Diabetes.co.uk, working references are 4 to 7 mmol/L before meals and under 8.5 mmol/L at least 90 minutes after eating.

Gestational diabetes — per Diabetes UK, the routine UK guidance is fasting under 5.3 mmol/L and one hour after meals under 7.8 mmol/L [9].

Pregnancy targets are noticeably tighter than for the general population because maternal glucose directly affects foetal growth.

Older adults — NICE NG28 explicitly recommends "consider relaxing the target HbA1c level on a case-by-case basis, with particular consideration for people who are older or frail" (per the NICE NG28 public summary already referenced in the HbA1c section).

A reminder — these are general references, and your actual targets are set by your endocrinology team based on individual circumstances.

What Should Be My Blood Glucose Level During Hypoglycaemia Or Hyperglycaemia?

Per Diabetes UK, "a hypo is when your blood sugar level, also called blood glucose level, drops too low. This is usually below 4mmol/l."

Severe hypoglycaemia is defined functionally as a hypo where you need help from another person to recover, or where you lose consciousness. Severe hypo is a medical emergency — dial 999 immediately.

On the high side, the NHS lists "Over 11 mmol/L" as the home-test threshold for high blood sugar 90 minutes or more after eating (already cited above). This is the threshold for elevated glucose, not a standalone DKA trigger.

Diabetic ketoacidosis (DKA) is a separate, symptom-based emergency. The NHS lists the warning signs as feeling sick, vomiting, stomach pain, breathing faster than usual, drowsiness, or fruity-smelling breath — dial 999 or go to A&E if these appear.

CGM devices can alarm when glucose drops or shifts rapidly, but the customisability, fixed thresholds, calibration requirements and pump-loop compatibility differ by brand — refer to each brand's documentation.

If you are unsure whether you have hit the threshold for medical help, NHS 111 can give non-emergency advice. For emergency signs, dial 999 directly.

How Do I Check And Track Whether I Hit My Glucose Targets?

The most common UK home test is BGM (a finger-prick blood glucose meter) — low cost and instant, but only a snapshot of one moment.

The CGM industry today includes Abbott FreeStyle Libre, Dexcom, Medtronic Guardian/Simplera and SIBIONICS among the major brands.

Each brand differs in regulatory framework (FDA / CE / MHRA), placement, wear duration, calibration requirement and pump compatibility — refer to each brand's official documentation.

Note: Medtronic Guardian 4 is typically used within hybrid closed-loop insulin delivery systems rather than as a standalone CGM.

Take SIBIONICS GS3 CGM as an example — per the official SIBIONICS product page, GS3 is a CE-certified CGM that can be worn for up to 14 days and updates a glucose reading every 5 minutes [10].

GS3 is sold in the European market and is not sold under the US FDA framework (per the SIBIONICS GS3 official user guide, GS3 uses factory calibration and does not require finger-prick calibration).

CGM measures glucose in interstitial fluid and there is a physiological lag relative to blood glucose (as noted earlier).

GS3, like other CGM devices, does not measure, calculate or display HbA1c — HbA1c must be obtained from a laboratory blood test.

Recommended testing moments for most home settings — on waking, before meals, two hours after meals, before bed, around exercise and any time you feel "off".

Whether you use BGM or CGM, comparing your daily trace against the seven targets above is the most direct way to judge whether you are on track.

Common Misconceptions About Glucose Targets

Misconception 1 — A normal fasting reading means everything is fine. Post-meal hyperglycaemia is independently linked to cardiovascular risk, and looking only at fasting glucose misses the daily peaks.

Misconception 2 — A normal HbA1c equals perfect management. HbA1c is an average and can mask sharp swings, so TIR and the coefficient of variation (CV) add a sense of "intra-day stability" — exactly what the ATTD consensus emphasised.

Misconception 3 — CGM and finger-prick readings should match exactly. Due to the physiological lag between interstitial fluid and blood (per PMC literature), the two can diverge visibly during rapid changes, which is not a device fault.

Misconception 4 — Lower is always better. Tightening targets too aggressively raises the risk of hypoglycaemia, especially in older adults and those with multiple comorbidities.

Misconception 5 — People without diabetes do not need to track glucose. A large number of UK adults have undiagnosed prediabetes, and periodic HbA1c review still works as an early signal.

If you want more detail, the AGP report shipped with mainstream SIBIONICS CGM devices presents your "time in range" visually for your clinician to interpret.

Verdict

Back to the original question — "what should my glucose be" — UK guidance is consistent: 4.0 to 5.4 mmol/L fasting and under 7.8 mmol/L at the two-hour mark for adults without diabetes.

For people with diabetes, your numbers are personalised by your clinical team on top of these references, and HbA1c plus TIR remain the long-term yardsticks.

No reference table replaces a conversation with your GP, diabetes specialist nurse or endocrinologist — age, pregnancy, comorbidities and medication can all shift your targets.

Next steps — log key time points with a home meter, and consider CGM if you need continuous five-minute readings around the clock.

Pair the curves with your diet, exercise and sleep patterns so you can spot your own "trigger foods" and "stabilising habits".

This article is informational and does not replace professional medical advice — any treatment changes should follow your doctor's guidance.

FAQ

Q: What is a normal blood sugar level UK chart?

A: For UK adults without diabetes, BHF references give 4.0–5.4 mmol/L fasting and below 7.8 mmol/L two hours after eating. The table for people with diabetes is in the Quick Answer section above.

Q: Is 7 mmol/L too high if I don't have diabetes?

A: Two hours after eating, 7 mmol/L sits inside the under-7.8 threshold and is usually fine.

Repeated fasting readings around 7 mmol/L are close to the NHS diabetes threshold (≥ 7 mmol/L fasting), so book a GP review and an HbA1c test.

Q: What level of blood sugar is dangerous in the UK?

A: Below 4 mmol/L is hypoglycaemia per Diabetes UK. Severe hypoglycaemia is defined functionally — when you need help from another person to recover or lose consciousness — and is a 999 emergency.

For high blood sugar, the NHS treats over 11 mmol/L on a home test 90 minutes or more after eating as elevated. DKA is identified by symptoms (sick, vomiting, fast breathing, fruity breath, drowsiness) rather than glucose level alone — seek emergency care if those appear.

Q: Why is my morning glucose higher than my bedtime glucose?

A: The common reason is the dawn phenomenon — early-morning surges of growth hormone and cortisol drive hepatic glucose output up. Discuss adjusting your long-acting insulin dose or your bedtime food with your team.

Q: Can a CGM tell me my HbA1c?

A: CGM does not measure HbA1c directly. Some apps estimate GMI (Glucose Management Indicator) from recent CGM data, but GMI and laboratory HbA1c can differ — your laboratory HbA1c remains the standard for clinical decisions.

SIBIONICS GS3 does not display A1C, and A1C must be obtained from a laboratory blood test.

Q: Are blood sugar targets the same for type 1 and type 2 diabetes?

A: Pre-meal targets are similar (4 to 7 mmol/L), but post-meal targets differ — type 1 aims for 5 to 9 mmol/L (per Diabetes UK), while type 2 working references are under 8.5 mmol/L (per Diabetes.co.uk).

Children, pregnant women and older adults each have their own specific targets.

References

[1] Schmelzeisen-Redeker G, et al. (2015). Time Delay of CGM Sensors: Relevance, Causes, and Countermeasures. Journal of Diabetes Science and Technology, 9(5), 1006–1015. https://pmc.ncbi.nlm.nih.gov/articles/PMC4667340/
[2] British Heart Foundation. (2024). Blood sugar levels: what is normal? Heart Matters Magazine. https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/tests/blood-sugar
[3] Diabetes.co.uk. (2024). Blood Sugar Level Ranges. https://www.diabetes.co.uk/diabetes_care/blood-sugar-level-ranges.html
[4] NHS. (2024). High blood sugar (hyperglycaemia). nhs.uk. https://www.nhs.uk/conditions/high-blood-sugar-hyperglycaemia/
[5] Monnier L, Colette C, Dejager S, Owens DR. (2013). Thirty Years of Research on the Dawn Phenomenon: Lessons to Optimize Blood Glucose Control in Diabetes. Diabetes Care. https://pmc.ncbi.nlm.nih.gov/articles/PMC3836156/
[6] Bellini A, et al. (2022). The Effects of Postprandial Walking on the Glucose Response after Meals with Different Characteristics. Nutrients, 14(5), 1080. https://pmc.ncbi.nlm.nih.gov/articles/PMC8912639/
[7] Diabetes.co.uk. (2024). What is HbA1c? — Definition, Units, Conversion, Testing & Control. https://www.diabetes.co.uk/what-is-hba1c.html
[8] Battelino T, et al. (2019). Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range. Diabetes Care, 42(8), 1593–1603. https://pmc.ncbi.nlm.nih.gov/articles/PMC6973648/
[9] Diabetes UK. (2024). How to check your blood sugar levels. https://www.diabetes.org.uk/about-diabetes/symptoms/testing
[10] SIBIONICS. (2026). SIBIONICS GS3 CGM Glucose Sensor for 24/7 Continuous Monitoring. https://www.sibionicscgm.com/products/sibionics-gs3-cgm-continuous-glucose-monitoring-system

Disclaimer

This article is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Author Information

This article was written by the SIBIONICS Professional Health Content Team. The author has years of research experience in CGM and diabetes management, helping users optimise their device experience through science-based practices.

Last Updated: May 15, 2026

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