Lab marker
Fasting glucose
FPG · Fasting plasma glucose
The base of every metabolic panel — a snapshot of glycaemia after an 8–12 hour fast.
What it measures
Plasma glucose concentration after at least 8 hours of fasting. Captures the basal hepatic glucose output balanced against peripheral uptake. Reported in mg/dL (US) or mmol/L (SI).
Reference context
4 guideline sources
WHO and ADA use slightly different lower thresholds for IFG (110 vs 100 mg/dL). HbA1c and fasting glucose can disagree — about 20% of adults with prediabetic HbA1c have normal fasting glucose, and vice versa. Both have value; an oral glucose tolerance test resolves ambiguity in borderline cases.
Population context — consult guideline targets below
Mechanism
Why moving this marker matters
Fasting hyperglycaemia indicates either reduced insulin sensitivity (peripheral tissues failing to clear glucose) or pancreatic beta-cell insufficiency. Both progress over years; fasting glucose typically moves later than fasting insulin / HOMA-IR but earlier than HbA1c crosses the diabetes threshold.
Guideline targets
What major guidelines recommend
ADA 2024 (normoglycaemia)
<100 mg/dL (<5.6 mmol/L)
ADA 2024 (impaired fasting glucose / prediabetes)
100–125 mg/dL (5.6–6.9 mmol/L)
ADA 2024 / WHO (diabetes)
≥126 mg/dL (≥7.0 mmol/L) on two separate readings
WHO 2006 (IFG, narrower cut-off)
110–125 mg/dL (6.1–6.9 mmol/L)
How to measure
The test, where to get it, when to repeat
Method
Standard fasting blood draw (8–12 hours of fasting; water is permitted). Plasma glucose preferred over capillary fingerstick for clinical decisions.
Where
Standard panel everywhere — included in routine GP preventive bloods.
Typical cost
Bundled in standard panel; €5–10 standalone.
Fasting
Required
When to test
USPSTF 2021
35–70Screen for prediabetes and type 2 diabetes in adults 35–70 with overweight or obesity; every 3 years if normal.
ADA 2024
35+Universal screening from age 35 in adults; annually if prediabetic, every 3 years if normal.
Where to test
Independent labs offering this test
Healicus refers you to independent laboratories. You order from the lab; they take the sample, run it, and return your result on their own platform. Healicus never sees your value.
Randox Health
UK · EU · INTLClinic-based premium panels — wider biomarker breadth than home-test brands.
Visit Randox Health
Synlab
DE · EU · INTLEurope-wide medical lab network — referrals via partner GPs and direct-to-consumer programmes where offered.
Visit Synlab
Medichecks
UKUKAS-accredited home blood-test panels with GP-equivalent biomarker coverage.
Visit Medichecks
Thriva
UKApp-first subscription home testing, capillary draw, clinician-reviewed reports.
Visit Thriva
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Context
Reading the numbers
WHO and ADA use slightly different lower thresholds for IFG (110 vs 100 mg/dL). HbA1c and fasting glucose can disagree — about 20% of adults with prediabetic HbA1c have normal fasting glucose, and vice versa. Both have value; an oral glucose tolerance test resolves ambiguity in borderline cases.
Caveats
Acute stress, illness, and recent corticosteroid use elevate fasting glucose. A single elevated reading warrants confirmation before diagnostic action.
Practices
What's been shown to influence this marker
PREDIMED and follow-up trials show 0.2–0.3 mmol/L reductions in fasting glucose with sustained adherence.
Mediterranean dietary pattern
Habit·Olive oil, fish, nuts, legumes, plants. The most-studied diet for cardiovascular and cognitive longevity.
Why
The Mediterranean pattern — heavy on plants, olive oil, fish, nuts, legumes; moderate fish and dairy; light on red meat — has the strongest evidence base of any specific diet for long-term cardiovascular and cognitive outcomes. PREDIMED, the largest trial, showed ~30% reduction in major cardiovascular events vs. low-fat control.
Slot in your day
How to do it
How
Olive oil as the primary fat. Plants at every meal. Fish 2–3× per week. Nuts daily (small handful). Red meat once a week or less. Wine optional, with food.
Sticking with it
Stock the kitchen for one week's pattern. Decisions live in the shopping list, not at mealtime.
Markers this may influence
Evidence
Post-meal walking
Habit·10–15 minute walk after meals blunts the post-prandial glucose spike.
Why
Light walking activates muscle glucose uptake without insulin signalling — the muscles pull glucose out of the blood directly. Short post-meal walks measurably reduce the glycemic peak vs. sitting after eating. Especially useful for those with prediabetes, insulin resistance, or after carb-heavy meals.
Slot in your day
How to do it
How
Walk 10–15 minutes within 30 minutes of finishing a meal. Slow pace is fine. Doesn't need to be every meal — the largest carb meal of the day is the highest-leverage one.
Sticking with it
Pair with the largest carb meal of the day — biggest leverage, easiest to remember.
Markers this may influence
Evidence
16:8 intermittent fasting
Habit·16-hour overnight fast, 8-hour eating window. Not new — monastic traditions have done it for centuries.
Why
A daily eating window of about 8 hours (e.g., noon to 8pm) with the rest of the day fasted. Often improves insulin sensitivity and reduces visceral fat in trials, though the mechanism is largely the spontaneous calorie reduction it produces rather than fasting per se. Easy entry-level intervention.
Slot in your day
How to do it
How
Skip breakfast or skip dinner. Black coffee, tea, water during the fast. No special protocol needed; consistency over weeks matters more than perfection on any one day.
Ideal for
People with metabolic syndrome, insulin resistance, or who tend to graze.
Sticking with it
Decide your eating window for the week, not the day. Drift is the failure mode.
Markers this may influence
Evidence
Reduce ultra-processed food
Habit·UPF intake correlates with mortality independent of total calories. The category, not just the calories, matters.
Why
Foods classified as ultra-processed (NOVA group 4) — packaged snacks, sweetened drinks, reformulated meats, ready meals — predict cardiovascular and all-cause mortality even after adjusting for total calories and macronutrient profile. Mechanisms include altered satiety signalling, additive effects, and displacement of whole foods.
Slot in your day
How to do it
How
Aim for the bulk of the diet to be foods you'd recognise in a kitchen 100 years ago. Convenience foods are fine occasionally; the issue is when they become the default.
Sticking with it
Don't fight cravings in front of the cupboard — fight them at the supermarket.
Markers this may influence
Evidence
See also
Related markers
Take to your physician
Worth discussing
- Whether fasting glucose, HbA1c, and your symptoms fit the prediabetes or diabetes definition.
- If in the IFG range, what intervention (DPP-style lifestyle programme, metformin discussion) is appropriate for your risk profile.
- Whether OGTT or fasting insulin would clarify a borderline picture.
Sources
Cited literature
- [1]USPSTF 2021 — Screening for prediabetes and type 2 diabetes in adults(2021)
- [2]ADA Standards of Care in Diabetes 2024(2024)
- [3]WHO/IDF — Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia(2006)
- [4]Salas-Salvadó et al., PREDIMED — prevention of diabetes with a Mediterranean diet(2014)
Edited by Carl Pöhl, MD · Healicus editorial
Last reviewed May 2026
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