Normal Blood Sugar Levels Chart for Adults (mmol/L)

Staring at a blood sugar result and wondering whether that number means something is one of those quiet moments of uncertainty almost everyone has faced. Between different units, conflicting advice online, and charts that seem to use a different scale every time, it is no wonder people feel lost. This guide uses the mmol/L measurement standard across Ireland and the UK, drawing directly on national health authority recommendations, so you can read any normal blood sugar levels chart with real confidence.

Normal fasting glucose (adult): 4.0–5.4 mmol/L (72–99 mg/dL) · Prediabetes fasting glucose: 5.5–6.9 mmol/L (100–125 mg/dL) · Diabetes fasting glucose: ≥7.0 mmol/L (≥126 mg/dL) · Normal HbA1c: <5.7% (39 mmol/mol)

Four key facts, one pattern: healthy blood sugar management depends on knowing which measurement you are looking at, because fasting, post-meal, and HbA1c targets are not interchangeable.

What is a normal blood sugar range for adults?

Fasting blood glucose targets

• Normal: 4.0–5.4 mmol/L (72–99 mg/dL) — Mayo Clinic (US medical centre)
• NHS Scotland guidance says normal for people without diabetes is 3.5–5.5 mmol/L before meals (MyDiabetesMyWay NHS Scotland)
• A fasting reading above 7.0 mmol/L signals possible diabetes — NHS (UK health authority)

Fasting glucose is the most standardised measure because food has not influenced the result. It gives the cleanest picture of how your body handles glucose at baseline.

Post-meal blood glucose targets

• Normal 2 hours after eating: <7.8 mmol/L (<140 mg/dL) — British Heart Foundation (UK cardiovascular charity)
• NHS Scotland sets the normal post-meal ceiling at <8.0 mmol/L (MyDiabetesMyWay NHS Scotland)
• NHS patient guidance says a home reading over 11.0 mmol/L at least 90 minutes after eating is considered high — NHS

The implication: a single high reading after a large meal is not automatically alarming, provided it drops back below the threshold within two hours. Persistent elevation after eating is a stronger signal.

HbA1c targets

• Normal: <5.7% (<39 mmol/mol) — MedlinePlus (US National Library of Medicine)
• British Heart Foundation gives the normal threshold as <6.0% (<42 mmol/mol) (British Heart Foundation)
• HbA1c reflects average glucose over the previous 2–3 months — Diabetes UK

Why this matters: HbA1c does not require fasting and captures long-term control. It is the measure most clinicians rely on for diagnosis and treatment decisions.

What is a pre-diabetic sugar level?

Fasting glucose in prediabetes

• Prediabetes fasting range: 5.5–6.9 mmol/L (100–125 mg/dL) — Mayo Clinic
• This range is sometimes called “impaired fasting glucose”
• A reading of 7.0 mmol/L or above on two separate tests indicates diabetes, not prediabetes

Prediabetes rarely produces symptoms. Many people discover it only through routine blood work.

HbA1c in prediabetes

• Prediabetes HbA1c: 5.7%–6.4% (39–46 mmol/mol) — MedlinePlus
• At 6.5% or higher, the diagnosis shifts to diabetes
• People in the prediabetic range have a heightened risk of progressing to type 2 diabetes without intervention

Risk factors for progression to diabetes

• Excess body weight, particularly around the abdomen
• Physical inactivity and a diet high in refined carbohydrates
• Family history of type 2 diabetes
• Metabolic conditions such as fatty liver — see also ALT SGPT High: Normal Range, Danger Zone, & How to Lower

The pattern: prediabetes is a reversible warning zone, not a fixed diagnosis. Lifestyle changes — even modest weight loss of 5–7% — can return glucose to normal range according to Diabetes UK.

Is 200 blood sugar normal?

What 200 mg/dL (11.1 mmol/L) means

• 200 mg/dL equals 11.1 mmol/L using the standard conversion (divide by 18)
• A single reading at this level after a very high-carb meal can occur in a non-diabetic person
• Consistent readings above 11.1 mmol/L two hours after eating meet the diagnostic criteria for diabetes — NHS

The context determines whether 200 is alarming. A random post-meal spike is different from the same number before breakfast.

Post-meal vs fasting context

• Fasting reading of 11.1 mmol/L: almost certainly diabetes — seek medical review
• Post-meal reading of 11.1 mmol/L within 1 hour: possibly normal after a large meal
• Post-meal reading of 11.1 mmol/L at the 2-hour mark: elevated and warrants investigation

When to seek medical advice

Is 8.7 blood sugar high?

Interpreting 8.7 mmol/L (156 mg/dL)

• 8.7 mmol/L is above the normal fasting ceiling of 5.4 mmol/L — Mayo Clinic
• It falls within the prediabetes fasting range (5.5–6.9 mmol/L) if taken before eating
• If taken 2 hours after eating, it exceeds the normal <7.8 mmol/L target but is below the 11.1 mmol/L diabetes threshold

The trade-off: 8.7 mmol/L is not an emergency number, but it is a clear signal that glucose regulation is not optimal.

Fasting vs random context

• Fasting 8.7 mmol/L: well above normal — suggests prediabetes or possible diabetes
• Random 8.7 mmol/L within 2 hours of eating: elevated but not diagnostic
• Random 8.7 mmol/L after 4+ hours of fasting: concerning — check with a formal fasting test

Urgency and next steps

What is a 6.2 blood sugar level equal to?

6.2 mmol/L in mg/dL

6.2 mmol/L = 111.6 mg/dL (multiply by 18.0182)

This falls into the prediabetes fasting range (100–125 mg/dL) according to Mayo Clinic.

Corresponding HbA1c estimate

• Estimated HbA1c for an average glucose of 6.2 mmol/L: approximately 6.5% (48 mmol/mol)
• This estimate uses the ADAG formula: HbA1c (%) = (average glucose in mmol/L + 2.59) / 1.59
• 6.5% is the diagnostic threshold for diabetes — MedlinePlus

Implications for diabetes diagnosis

HbA1c to estimated average glucose conversion

Eight HbA1c values, one pattern: each 1% rise in HbA1c corresponds to roughly a 1.6 mmol/L increase in average glucose, making the conversion predictable enough for daily use.

Why this matters: the conversion table lets you move between HbA1c and daily glucose numbers. If your lab gives you an HbA1c of 7.0%, your average daily glucose has been running around 8.6 mmol/L — a figure that matters for setting day-to-day targets.

How to use a normal blood sugar levels chart

Step 1: Identify your test type

• Fasting glucose: no food or drink (except water) for at least 8 hours
• Post-meal glucose: measured 2 hours after the start of a meal
• HbA1c: no fasting required; reflects 2–3 month average

Step 2: Find the correct column on your chart

• Check whether the chart uses mmol/L (standard in Ireland, UK, Canada, Australia) or mg/dL (standard in the US)
• Conversion: 1 mmol/L = 18 mg/dL
• Use the chart that matches your device’s display unit

Step 3: Compare your result against the appropriate target

• Normal fasting: 4.0–5.4 mmol/L — MyDiabetesMyWay NHS Scotland
• Normal post-meal: <7.8 mmol/L — British Heart Foundation
• Normal HbA1c: <5.7% — MedlinePlus

Step 4: Look for patterns, not single readings

• One high reading after a celebration meal is not a crisis
• Three or more consistent out-of-range readings within a week signal a trend
• Track readings in a log or app to share with your GP

What is clear and what remains uncertain

What experts say about blood sugar targets

For people with type 1 diabetes, the HSE recommends a fasting glucose target of 5–7 mmol/L and a before-bed target of 5–9 mmol/L.

— HSE Ireland guidance

HbA1c reflects the average amount of glucose in your blood over the last two to three months. An ideal HbA1c level for a person with diabetes is 48 mmol/mol (6.5%) or below.

— Diabetes UK (UK diabetes charity)

For people without diabetes, normal blood glucose is 3.5 to 5.5 mmol/L before meals and less than 8 mmol/L two hours after meals.

— MyDiabetesMyWay NHS Scotland

The suggested pre-meal target blood glucose range is 4.0 to 8.0 mmol/L, and the suggested 2-hour post-meal target range is 5.0 to 10.0 mmol/L.

— MyHealth Alberta (Canadian health authority)

Four authorities, four slightly different target ranges — reflecting the difference between diagnostic thresholds (what defines normal) and treatment targets (what clinicians aim for in people already diagnosed). Knowing which one you are looking at changes how you interpret the number.

A normal blood sugar levels chart gives you a framework, but no chart replaces a conversation with a healthcare professional. The most practical takeaway: understand your own reading’s context — fasting or post-meal, mmol/L or mg/dL, diagnostic criteria or treatment target — and use that context to decide whether a single number is a signal worth acting on. For anyone reading this in Ireland or the UK, the guidance is clear: a fasting glucose below 5.5 mmol/L and an HbA1c below 5.7% put you in the healthy zone. If you are above those thresholds, the choice is straightforward — act now with lifestyle changes, or wait and face a steeper climb later.

Frequently asked questions