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Understand why HbA1c is the gold standard for type 2 diabetes testing, what normal levels are, and how you can maintain them.

Author: Leanne Edermaniger

May 20, 2024

Reviewed by: Dr Thom Phillips

In this article:

What is HbA1c?

A haemoglobin A1C or HbA1c blood test tells you your average blood sugar levels over the last 90 days. It is used to diagnose and monitor type 2 diabetes.

A HbA1c test measures glycated haemoglobin. When haemoglobin, the protein within your red blood cells responsible for transporting oxygen around the body, joins with glucose, it becomes glycated[1].

Because red blood cells live for about 3 months, the HbA1c test will reflect the red blood cells currently in circulation and provide an average blood sugar reading.

Why test HbA1c?

An HbA1c test is used to detect or monitor diabetes or determine your body’s response to diabetes medication.

Rather than give you a glucose reading at a single point in time, the HbA1c tells you about your average reading over 2 to 3 months. Therefore, HbA1c testing is the gold standard for identifying, monitoring, and treating type 2 diabetes[2].

HbA1c can diagnose prediabetes, a state where your average blood sugar levels are higher than they should be but not high enough to diagnose type 2 diabetes. However, having prediabetes increases your risk of developing type 2 diabetes and other health complications, including heart disease and strokes[3].

How to test HbA1c

An HbA1c is a blood test. You can test your HbA1c level with our HbA1c (pre-diabetes) Blood Test at home.

Once ordered, we will send out an at-home test kit which contains everything you need to provide a blood sample using a finger-prick test. Alternatively, you can arrange a home nurse appointment or visit a partner clinic to provide a full venous blood sample instead.

Once our partner lab has received your sample, you should receive your results within 2 working days.

What is a good HbA1c level?

According to our lab, a healthy HbA1c level is between 20 and 42 mmol/mol or less than 6%.

The NHS states that a high HbA1c is 48 mmol/mol and above[4].

At Forth, our data shows that the average HbA1c level for our customers is 35 mmol/mol, but this can also be split by sex:

  • Women: 34.8 mmol/mol
  • Men: 35.3 mmol/mol

What is the normal HbA1c level by age?

Our data shows that the average HbA1c level for each age group are as follows:

Age Average HbA1c (mmol/mol)
18 – 29 32.8
30 – 39 33.6
40 – 49 34.7
50 – 59 35.4
60+ 38.5

Symptoms And Impact Of Low Hba1c

A low HbA1c could signify low blood sugar levels (hypoglycaemia) and cause symptoms that include:

  • Dizziness
  • Hunger
  • Sweating
  • Anxiety or irritability
  • Shaking
  • Heart palpitations
  • Tiredness or weakness
  • Vision changes
  • Confusion[5]

A low HbA1c level may indicate underlying diseases such as anaemia or chronic kidney disease. If you have a low HbA1c level, below 20 mmol/mol or less than 4%, you should speak to a doctor for further advice.

Ideally, your HbA1c should be <42 mmol/mol or less than 6%. If your levels are 6 to 6.4% or between 42 and 47 mmol/mol this could be indicative of diabetes. A level higher than 48 mmol/mol or 6.5% is used to diagnose type 2 diabetes.

Symptoms And Impact Of High Hba1c

If you have a high HbA1c, it is a sign that your average blood sugar levels have been high for at least 2 to 3 months.

You may have been experiencing type 2 diabetes symptoms before receiving your HbA1c results, such as:

  • Extreme thirst
  • Feeling very tired
  • Needing to pee more often, especially at night
  • Blurred vision
  • Recurrent thrush or itchy genitals
  • Unexplained weight loss
  • Wounds take longer to heal than usual [6]

A high HbA1c level is a sign that you are at a raised risk of experiencing diabetes complications, including:

  • Cardiovascular disease includes heart attacks, peripheral arterial disease, and strokes
  • Kidney disease is caused by diabetic nephropathy or high blood pressure and may require dialysis or transplantation if left untreated.
  • Retinopathy affects more than 25% of type 2 diabetic patients and diabetes is the leading cause of preventable sight loss.
  • Peripheral neuropathy can cause burning, numbness, and tingling in the hands and feet and can lead to persistent neuropathic pain.
  • Foot problems are caused by peripheral neuropathy and peripheral arterial disease. If left untreated it can lead to limb or life-threatening complications[7].

By regularly monitoring your HbA1c levels, you can help minimise the risk of complications and maintain your blood sugar levels within a healthy range.

Managing your HbA1c Levels

A healthy HbA1c level generally means your blood sugar levels are well maintained and reduces your risk of either developing diabetes or diabetic complications.

The recommended HbA1c target for people with diabetes is 48 mmol/mol (6.5%) [8]. There are many things you can do to help keep your HbA1c levels within a normal range. Keeping your average blood sugar levels down will likely require you to make several lifestyle changes.

Some of the things you can do include:

  • Exercise is a great way to lower blood glucose levels because it helps to use up stored energy and fat, while muscle contractions encourage the increased uptake of circulating sugar and improve insulin sensitivity[9].
  • Weight loss if you are overweight can have a big impact on your HbA1c levels. Previous research has shown improvements in HbA1c, blood pressure, and cholesterol levels for every 1 kilogram of body weight lost[10].
  • Reduce exposure to stress because feeling pent up or anxious can keep your blood sugar at consistently high levels, increasing your risk of complications.
  • Get restful sleep because not getting enough or poor sleep can have an adverse effect on blood sugar levels.
  • Keep your alcohol intake low because many alcoholic drinks contain carbohydrates, have a high sugar content, or contain a lot of calories which can contribute to weight gain and increase your blood sugar. You should also be aware that alcohol can quickly drop your blood glucose levels causing hypoglycaemia[11].

What food to eat/avoid for good HbA1c

Diet is a contributing factor to HbA1c levels and type 2 diabetes. Carbohydrates affect your blood sugar levels, so it’s important to understand which foods contain carbs and choose healthier options while being aware of your portion sizes.

The glycaemic index (GI) is one way to manage diabetes because it tells you how quickly a food will increase your blood glucose levels. The GI runs from 0 to 100 with 100 being the highest GI. Foods that contain slowly absorbed carbohydrates usually have a GI below 55[12].

Low GI Moderate GI High GI
Fruit:  apples, blueberries, blackberries, cherries, grapefruit, p Fruit: green bananas, kiwi, mango, grapes Fruit: pineapple, watermelon, dried dates, yellow (ripe) banana
Beans & legumes: butter beans, chickpeas, green beans, kidney beans, pinto beans, lentils, hummus Beans & legumes: canned beans e.g., kidney or pinto beans Vegetables: potato, parsnips, winter squash
Grains: Barley, bulgur wheat, wild rice, wholewheat pasta Grains: brown and white rice, couscous, white pasta Bread & grains: white and wholegrain bread, baguettes, bagels, rice
Vegetables: asparagus, avocado, broccoli, cabbage, celery, spinach, kale Vegetables: sweet potato, carrots, corn on the cob Drinks: sweetened tea/coffee, fruit juice, fizzy soda
Other foods: plant milk, lean red meat, poultry, shellfish, eggs Snacks: chocolate, muffins, popcorn Snacks: cakes, biscuits, crisps, doughnuts, rice crackers, cookies

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

- Health scores calculated


Article references

  1. Imai, C. et al. (2021) ‘Adherence to guideline-recommended hba1c testing frequency and better outcomes in patients with type 2 diabetes: A 5-year retrospective cohort study in Australian General Practice’, BMJ Quality & Safety, 30(9), pp. 706–714. doi:10.1136/bmjqs-2020-012026.

  2. Singh, B. et al. (2023) ‘A step in the right direction: Exploring the effects of aerobic exercise on hba1c reduction’, The Egyptian Journal of Internal Medicine, 35(1). doi:10.1186/s43162-023-00247-8.

  3. Morris, E. et al. (2020) ‘Effect of weight loss on cardiometabolic risk: Observational analysis of two randomised controlled trials of community weight-loss programmes’, British Journal of General Practice, 71(705). doi:10.3399/bjgp20x714113.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services