Case study · Diabetes · Published 26 October 2026
People with type 2 diabetes who started continuous glucose monitoring (CGM) through a Promatica delivered primary care service saw their HbA1c fall by 17.7 mmol/mol on average within six months. Fewer needed insulin, fewer needed other glucose lowering medicines, and medication spend did not rise.
At a glance
Practices
55 GP practices, 452,769 registered patients
HbA1c fall, new to CGM
17.7 mmol/mol on average
Reaching HbA1c below 64 mmol/mol
17% before, 45% after
On insulin, new to CGM
88% before, 76% after
HbA1c fall after moving from another CGM system
4.8 mmol/mol on average
Change in monthly medication cost
None
The challenge
Across the 55 participating practices, 27,568 people live with diabetes (6.1% of registered patients), and 92.6% of them have type 2. Most carry more than diabetes: 83% of people with type 2 are overweight or obese, nearly a quarter have chronic kidney disease or cardiovascular disease, and 44% have two or more of these conditions.
Continuous glucose monitoring can transform day to day control, but the people who stand to gain most are spread thinly across practice lists. Finding them, starting them on CGM within current NICE eligibility, and then showing whether it worked all depend on data that already sits in the GP record.
What we did
Promatica delivers a CGM service in primary care, working in partnership with a CGM manufacturer and participating GP practices.
Identify. PRISM, our population health platform, reads coded GP records through NHS assured IM1 integrations with EMIS Web and SystmOne, and finds the patients who meet CGM eligibility criteria.
Start. Eligible patients are invited and started on CGM within their usual practice care.
Evaluate. Six months on, PRISM uses the same routine records to compare each person’s results before and after starting, with no extra data collection for the practice.
The evaluation looked at two groups: 125 people with type 2 diabetes who had never used CGM, and 146 people (82 with type 1, 64 with type 2) who moved from another CGM system.
Results: people new to CGM
In people with type 2 diabetes starting CGM for the first time, average HbA1c fell from 85.1 to 67.4 mmol/mol, and nearly three in four improved by at least 5.5 mmol/mol. This was a group with long standing, hard to control diabetes: 15 years since diagnosis on average, and 88% already on insulin.
| Measure | Before | After |
|---|---|---|
| Average HbA1c (mmol/mol) | 85.1 | 67.4 |
| HbA1c below 64 mmol/mol | 17% | 45% |
| HbA1c below 53 mmol/mol | 8% | 23% |
| On any insulin | 88% | 76% |
| On other glucose lowering medicines | 79% | 66% |
The improvement held in every group with enough results to test, including people with chronic kidney disease (down 16.1 mmol/mol), cardiovascular disease (down 13.7) and two or more long term conditions (down 11.8). Referrals to secondary care also fell. All changes shown are statistically significant (p < 0.05).
Results: people moving from another CGM system
People who moved to the service from another CGM system saw average HbA1c fall from 70.6 to 65.8 mmol/mol, a reduction of 4.8 mmol/mol, with 48% improving by at least 5.5 mmol/mol. A smaller change is expected here, because these people were already using CGM.
The clearest gains were in type 2 diabetes: HbA1c fell by 5.8 mmol/mol and GP visits fell by 15%, from 1.79 to 1.52 a month. In type 1 diabetes, HbA1c fell by 3.7 mmol/mol, though the group was too small for this to reach statistical significance.
Prescribing cost
Monthly medication cost did not change in either group, despite the shift away from insulin and other medicines in people new to CGM. The main change in prescribing cost was the sensors themselves: about £66 a month for people starting CGM, and about £17 a month more for people moving from their previous CGM system. These figures, based on NHS prices for items issued, do not count any savings from fewer GP visits or referrals.
About the evaluation
This is a before and after service evaluation using routine GP records, in which each person acts as their own comparison over the six months before and after starting the service. There was no separate control group, so other changes in care may have contributed. Only people with a result recorded both before and after are included in each comparison: HbA1c was available for 53 people new to CGM and 62 people who moved from another CGM system. The evaluation was carried out by Promatica Digital in October 2026.
Work with us
For the NHS
PRISM helps practices and PCNs find the patients most likely to benefit from a new pathway, then shows the outcomes from the records you already keep.
For life sciences
We design and deliver primary care programmes that generate real world evidence from routine GP data, under NHS information governance.