01Purpose and principlesWhat the assessment is for and the core concepts behind it.
HbA1c integrates glucose exposure over red-cell life. Capillary testing gives a point value; CGM adds direction, time in range, time below range and variability. Each answers a different question, and discordance is clinically useful rather than an inconvenience to ignore.
Tight control can reduce microvascular complications over time, but benefit is delayed whereas hypoglycaemia is immediate. Frailty, cognitive impairment, limited life expectancy, renal failure, recurrent falls and dependence on carers may shift the priority toward avoiding symptoms and severe events.
The central decision is what target and monitoring method will change management safely for this person. Goals must be revisited after severe hypoglycaemia, pregnancy, new comorbidity, loss of self-management capacity or a major treatment change.
Key points
- A target is a shared clinical decision, not a performance grade; balance microvascular benefit against hypoglycaemia, frailty, comorbidity, treatment burden and the person's priorities.
- For most adults with type 1 diabetes NICE supports HbA1c 48 mmol/mol or lower when achievable safely; technology and education should support, not coerce, that goal.
- For type 2 diabetes, NICE target choice depends partly on whether treatment can cause hypoglycaemia, and targets should be relaxed when harms outweigh likely long-term benefit.
- HbA1c estimates recent glycaemic exposure but hides variability and hypoglycaemia; pair it with capillary or CGM data when treatment decisions require patterns.
- Anaemia, haemoglobin variants, recent transfusion, pregnancy, advanced kidney disease and altered red-cell lifespan can make HbA1c misleading.
- Offer adults with type 1 diabetes a choice of real-time or intermittently scanned CGM, with education, alarm settings and an alternative capillary meter.
- Routine self-monitoring in non-insulin-treated type 2 diabetes is not universally helpful, but becomes appropriate for hypoglycaemia-risk medicines, pregnancy, acute illness, driving or structured treatment changes.
- Review fasting, post-meal, overnight and exercise patterns; avoid responding to every isolated reading with unplanned correction insulin.
- Driving rules, occupational risk and impaired hypoglycaemia awareness may require higher operational glucose thresholds than the long-term HbA1c target suggests.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
A motivated person with long life expectancy, preserved awareness and low treatment burden may pursue guideline HbA1c and CGM goals when they can do so without recurrent hypoglycaemia.
Frailty, cognitive decline, advanced multimorbidity, falls, severe hypoglycaemia or reliance on inconsistent carers favours a simpler regimen and higher glucose range focused on safety.
Reduced awareness, nocturnal episodes, seizure, third-party assistance, fear-driven restriction or recurrent time below range requires urgent education, target and medicine review rather than congratulation for a low HbA1c.
An HbA1c that conflicts with glucose logs should prompt review of anaemia, haemoglobinopathy, transfusion, kidney disease, erythropoietin, pregnancy, assay interference and sensor accuracy.
A satisfactory average with repeated peaks and lows signifies unstable control. Insulin timing, meal estimation, exercise, lipohypertrophy or excessive corrections may be more important than increasing total dose.
Alarm fatigue, skin reaction, cost, data access, distress or inability to operate a device can negate benefit. Offer training, accessible alternatives and shared choice rather than declaring non-adherence.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Laboratory HbA1cFirst step - Why
- Estimate longer-term glycaemic exposure and track complication risk.
- Interpretation and limitations
- Interpret against the individual target and clinical context, not a universal pass mark. A rapid fall, recurrent lows or discordant home data can represent harm despite numerical improvement.
- 02
Capillary blood glucose profile - Why
- Link readings to meals, insulin, activity, symptoms and driving.
- Interpretation and limitations
- Use a structured question-led profile rather than random testing. Verify low or rapidly changing CGM values when symptoms disagree, and record hand cleanliness and strip quality if readings are implausible.
- 03
Continuous glucose monitoring report - Why
- Quantify time in, above and below range, variability and repeated daily patterns.
- Interpretation and limitations
- Review data completeness, target range, hypoglycaemia and overnight traces before average glucose. Pregnancy and paediatric ranges differ; use the locally supported metrics and not a generic dashboard target.
- 04
Full blood count and haematinics - Why
- Identify altered red-cell turnover that biases HbA1c.
- Interpretation and limitations
- Iron deficiency can raise HbA1c while haemolysis or recent blood loss can lower it. Correct the cause and use glucose-based monitoring until HbA1c becomes representative again.
- 05
Renal function and urine albumin - Why
- Identify hypoglycaemia risk and chronic kidney disease affecting targets or medicines.
- Interpretation and limitations
- Reduced insulin clearance and renally excreted drugs increase hypoglycaemia risk. Advanced CKD, anaemia and erythropoietin can weaken HbA1c reliability, making CGM or capillary patterns more valuable.
- 06
Hypoglycaemia awareness assessment - Why
- Detect impaired warning symptoms and severe-event risk.
- Interpretation and limitations
- Use a validated score alongside event history and CGM. Impaired awareness should trigger avoidance education, technology and driving advice; do not simply raise HbA1c without addressing causation.
- 07
Meter, sensor and injection-site review - Why
- Exclude technical and delivery problems before escalating therapy.
- Interpretation and limitations
- Compare meter with laboratory glucose when indicated, inspect sensor placement and injection sites, confirm insulin storage and observe technique. Lipohypertrophy produces erratic absorption and should not be injected into.
04Clinical next stepsHow the result changes management or prompts escalation.
01Set targetShared glycaemic goalFirst stepDiagnosis, annual review, pregnancy planning or a major health change.+
- 1Clarify diabetes type, complication risk, life expectancy, frailty, cognition, hypoglycaemia history, occupation, driving, support, treatment burden and what outcomes matter to the person.
- 2Use the relevant NICE starting target, then document why it is retained or modified and which outcomes—HbA1c, symptoms, time below range or severe events—will define success.
- 3Choose medicines and monitoring capable of reaching the goal safely, prioritising education and low-hypoglycaemia options when risk is high.
- 4Agree a review interval and explicit triggers for earlier reassessment, including severe hypoglycaemia, steroid treatment, pregnancy, acute illness or declining self-management capacity.
02DiscordanceHbA1c and glucose do not matchLaboratory HbA1c conflicts materially with capillary or CGM patterns.+
- 1Confirm that dates, units and device data are correct and compare readings with symptoms, meals, insulin and a contemporaneous laboratory glucose.
- 2Check blood count, iron or B12 status, kidney function, transfusion, haemolysis, pregnancy and known haemoglobin variant, and ask the laboratory about assay interference.
- 3EscalationBase short-term treatment on reliable glucose patterns while the HbA1c distortion is investigated; avoid dose escalation from a falsely high number.
- 4AlternativeDocument the limitation prominently and select an alternative monitoring plan with diabetes or laboratory specialists when distortion is ongoing.
03HypoglycaemiaProtect before intensifyingRecurrent glucose below range, severe event or impaired awareness.+
- 1Review event timing, insulin or sulfonylurea exposure, renal function, meals, alcohol, exercise and injection sites; give immediate driving and occupational safety advice.
- 2Temporarily relax targets where necessary, reduce the responsible medicine and provide structured hypoglycaemia-avoidance education rather than treating each episode only with carbohydrate.
- 3Offer CGM alarms, pump or hybrid closed-loop review and glucagon access according to diabetes type and eligibility, involving family or carers with consent.
- 4Reassess awareness and severe-event frequency after avoidance; refer persistent problematic hypoglycaemia to a specialist service.
04FrailtySimplify for safetyCognitive or functional decline, limited prognosis, falls or dependence on carers.+
- 1Define a symptom-avoidance glucose range and minimise finger-prick or injection burden while preventing ketosis in insulin-deficient diabetes.
- 2Deprescribe high-risk treatment carefully, simplify insulin timing and align administration with reliable meals and available carers; never remove essential basal insulin from type 1 diabetes.
- 3EscalationWrite a plan for hypoglycaemia, missed meals, acute illness and escalation that care staff can follow, including who supplies and checks equipment.
- 4Review after transitions of care, weight loss, kidney decline or recurrent infection because requirements can fall rapidly.
05Procedure and medicine safetyRelevant preparation, treatment and contraindications.
Fast-acting oral glucose
Use 15 to 20 g, recheck after 10 to 15 minutes, and repeat if still low.Use the individual's plan for children, pregnancy or pump systems. Chocolate and high-fat foods act slowly; follow recovery with longer-acting carbohydrate when the next meal is distant.
Glucagon
Administer the licensed rescue formulation by trained family, carer or clinician.Effect may be reduced after prolonged fasting, alcohol or depleted glycogen. Call emergency services, place safely, monitor recovery and investigate every event.
Insulin or sulfonylurea reduction
Adjust the implicated dose using documented glucose patterns and specialist advice when needed.Do not make blind percentage changes or withdraw basal insulin in type 1 diabetes. Renal decline, weight loss and meal change may require repeated adjustment.
06Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Measure HbA1c at the NICE interval, more often after treatment change or poor control and less often once stable, while recognising conditions that invalidate it.
- At every review ask about symptomatic, nocturnal and severe hypoglycaemia, impaired awareness, driving and fear; device summaries alone miss unrecorded events and distress.
- For CGM, review sensor wear, time below range, time in range, variability, overnight patterns, alarms and confirmatory testing supplies before altering medicines.
- Track treatment burden, eating disorder symptoms, mood, cognition, dexterity, sight, health literacy and carer capacity because these determine whether the plan is achievable.
- Link glucose goals with annual kidney, retinal, foot and cardiovascular risk review; an excellent HbA1c does not replace complication screening.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Average can conceal danger
An HbA1c near target can be produced by frequent highs balanced by frequent lows. Time below range and variability reveal a very different safety profile.
Finger-pricks remain relevant
People using CGM still need a compatible capillary meter for sensor failure, rapid change, driving requirements and readings that do not fit symptoms.
Target and threshold differ
A long-term HbA1c goal is not the same as a minimum safe glucose for driving, exercise or sleep. Operational thresholds need explicit education.
Kidney decline lowers requirements
Reduced clearance of insulin and some medicines can produce new hypoglycaemia before anyone recognises CKD progression; review doses rather than simply adding snacks.
Numbers can cause distress
Language such as 'in range' and 'above range' is more useful than 'good' and 'bad'. Data should support decisions, not moral judgement or punitive surveillance.
One target will not last forever
Pregnancy, frailty, steroids, remission, advanced complications and new occupations all change the balance of benefit and harm; document planned reconsideration.
08Common pitfallsFrequent interpretation and management errors.
- 01
Celebrating a low HbA1c without asking about severe or nocturnal hypoglycaemia.
- 02
Escalating treatment from HbA1c when anaemia or transfusion makes it unreliable.
- 03
Using random capillary readings without linking them to food, activity or medicine.
- 04
Removing access to finger-prick testing because a person uses CGM.
- 05
Keeping an intensive target after frailty or cognitive decline changes the risk balance.
- 06
Treating device non-use as non-compliance without exploring access, skin and distress barriers.