How fast can HbA1c come down?

Reviewed by the JForH team · 2026-10-30

HbA1c follows your glucose with a lag. A 2016 analysis found about half of a change shows within about 30 days and about 80% within 50–70 days, so a test three months after a change shows most of the effect. NICE advises testing every 3 to 6 months until stable. How far it falls depends on your starting level, your medicines and how much your weight and food change. Low-calorie soups and shakes diets lowered glucose within a week in one study.

How quickly can HbA1c come down?

Your glucose can drop within days of a change. HbA1c catches up over the following two to three months.

A 2016 analysis in the Journal of Diabetes Science and Technology found about 50% of a change in HbA1c happens in about 30 days, and about 80% in 50 to 70 days.

A worked example: if your HbA1c is 69 mmol/mol (8.5%) and your changes would settle it at 53 mmol/mol (7.0%), you might see around 61 after a month and around 56 after two. These are illustrations, not promises.

Why does HbA1c take three months to change?

HbA1c measures glucose stuck to haemoglobin in red blood cells. Diabetes UK explains that red blood cells are active for around 2 to 3 months, which is why the test is usually done quarterly. As older cells are replaced, the number moves towards your new average. Recent weeks count for more than older ones.

How often will my GP check my HbA1c?

NICE NG28 advises every 3 to 6 months until your HbA1c is stable on unchanging treatment, then every 6 months. Diabetes UK says most people are tested every 3 to 6 months, and you're entitled to at least one test a year.

A test sooner than about 3 months after a change will only show part of the effect. That's not a sign it isn't working.

How much can HbA1c drop in 3 months?

It depends on where you start and what changes. People with a higher HbA1c usually see bigger drops. Some reference points:

• Metformin alone lowers HbA1c by about 1.1 percentage points on average, about 12 mmol/mol, compared with a dummy pill (a 2012 pooled analysis of trials).
• Weight loss has the biggest effect. In the DiRECT trial, 86% of people who lost 15 kg or more were in remission at 12 months.

Do soups and shakes lower HbA1c fast?

They lower glucose very quickly. In the Newcastle Counterpoint study, 11 people with type 2 diabetes on a 600-calorie-a-day diet saw their fasting glucose fall from 9.2 to 5.9 mmol/L within one week. That was a small, short study.

The larger DiRECT trial in UK GP surgeries used soups and shakes at 825–853 calories a day for 3 to 5 months, then brought food back gradually. People had been diagnosed within 6 years. They lost 10 kg on average, and 46% were in remission at 12 months, against 4% of the comparison group.

What is the NHS Path to Remission Programme?

It's the NHS England version of this approach. It lasts a year, starting with about 12 weeks of soups and shakes, then food reintroduction, then support to keep the weight off. In North East London, for example, you may be eligible if you:

• are 18 to 65
• were diagnosed with type 2 diabetes in the last 6 years
• have a BMI over 27, or over 25 if you're from a Black, Asian or minority ethnic background
• don't use insulin

Referral is through your GP. In the first 1,740 people who started, 55% completed the programme and lost an average of 10.3 kg. Of those who completed and had their HbA1c checked, 32% were in remission.

What counts as remission?

An HbA1c below 48 mmol/mol (6.5%) at least 3 months after stopping all diabetes medicines, under the 2021 international definition. Stopping medicines must be done with your GP, never on your own.

Is it safe to bring HbA1c down quickly?

Diabetes UK advises lowering HbA1c in stages rather than with a sudden large drop. If you take insulin or gliclazide, eating much less can cause hypos, so your medicines may need changing before you start. In DiRECT, medicines were adjusted by the GP team at the start. Speak to your GP before any very low calorie diet.

How do I convert HbA1c between mmol/mol and %?

UK labs report mmol/mol, but many websites use %. These pairs follow the IFCC conversion, mmol/mol = (% minus 2.15) × 10.929:

What HbA1c should I aim for?

Your GP may set a looser target if you're older or frail.

What else can bring HbA1c down sooner?

• Take your medicines every day as prescribed.
• Cut back on starchy portions such as bread, potatoes, rice and pasta, and on sugary drinks.
• Walk after meals, even for 10 minutes.
• Lose weight if you can. Even a few kilograms helps.

Illness, steroid medicines and stress can push HbA1c up for a while, Diabetes UK notes. If a result surprises you, tell your GP what's been going on.

See what's moving your HbA1c (free check)

Last updated: 2026-10-30. Educational information, not medical advice. Talk to your doctor before changing your treatment.