Skip to navigation

Diabetes: Immune system health

Diabetes: Immune system health

Each year the number of people diagnosed with diabetes rises. In 2019, for instance, there were 100,000 more people living with a diabetes diagnosis in the UK than the previous year (i).
Currently, the charity Diabetes UK estimates one in 15 people in the UK has diabetes – this includes a million people who have type 2 diabetes but haven’t been diagnosed (ii). If the numbers keep rising at this rate, more than five million people are expected to have diabetes by 2025.
A condition caused by having too much sugar (glucose) in your blood, diabetes also has several well-known complications, such as problems with your heart, eyes, feet and kidneys. One complication, however, that’s arguably less well known is the effect diabetes can have on your immune system, particularly if you’re not having treatment (if you haven’t yet been diagnosed, for instance) or if your diabetes has been diagnosed but isn’t well controlled.

What is the difference between Type 1 and Type 2 Diabetes?

There are two main types of diabetes.

Type 1 diabetes

It typically starts in children and young adults, though it can develop in people of any age. It happens when your body stops making insulin, the hormone made by your pancreas that your body needs to regulate its blood sugar levels. In the UK, around one in 300 people develops type 1 diabetes (iii), which is the equivalent of about eight per cent of all people with all types of diabetes (iv).
We still don’t know exactly what causes type 1 diabetes, though in most cases it’s thought to be an autoimmune disease. This means that, in the case of diabetes, your immune system makes antibodies – which normally fend off harmful micro-organisms such as viruses and bacteria – that mistakenly attack and destroy insulin-making cells (beta cells) in your pancreas.
Some of these damaged beta cells may be replaced by new cells, or they may re-form using the process of cell division. But more cells are destroyed than replaced, and when you lose around 20 per cent of these beta cells your pancreas simply can’t make enough insulin to keep your blood sugar levels under control (v). So to stay healthy, you need regular insulin injections for the rest of your life.
Experts aren’t sure why this happens in some people but not others, though some believe it could be a virus that triggers the immune system to act in this way (iii).

Type 2 diabetes

Type 2 diabetes on the other hand, is more common in people aged 40 or older (or if you’re of South Asian origin, aged 25 or older), though more and more younger people are becoming affected by it too (vi).
If you have type 2 diabetes it means your pancreas is making insulin but not enough to keep your blood sugar levels normal, or that your cells can no longer use insulin properly, which is called insulin resistance (with insulin resistance, you need more insulin than usual because your body has become resistant to normal levels). Some people with type 2 diabetes don’t make enough insulin and have insulin resistance at the same time.
Experts still don’t know why some people develop type 2 diabetes, but several lifestyle factors may be involved, including being overweight and inactive, having type 2 diabetes in your family, having high blood pressure or a history of heart attack or stroke. Your age can be significant too, since the older you are, the higher your risk is of having type 2 diabetes.
While type 1 diabetes is often described as an autoimmune disease, type 2 diabetes is classed as a metabolic disease (that is, it’s one of several conditions that disrupt your metabolism, which is how your body gets or makes energy from the food you eat).
Both types of diabetes, however, are thought to have an effect on your immune system if your blood sugar levels are allowed to remain high or uncontrolled over time, which is known as chronic hyperglycaemia.

How does diabetes  affect the immune system?

People living with any type of diabetes are thought to be more susceptible to infections, including infections that are difficult to treat. This is because having a high blood sugar level reduces the immune system’s ability to protect the body against invading bacteria, viruses, fungi, toxins and parasites.
Scientists believe they’ve discovered several mechanisms whereby chronic hyperglycaemia might weaken your immune defence (vii), including the following:

  1. Persistent high blood sugar levels increase your risk for atherosclerosis, where fat deposits called plaque accumulates inside your blood vessels. These deposits make your blood vessels more narrow, which is bad for your heart but also causes a couple of problems where your immune system is concerned. First, it increases your risk of infections because the white blood cells made by your immune system find it more difficult to reach sites of infections caused by bacteria, viruses and other harmful micro-organisms and combat them effectively. Plaque in your blood vessels also slows down blood flow, which can lead to problems with wound healing and makes wounds more susceptible to infection.

  2. The fact that chronic hyperglycaemia slows down the rate at which blood flows through the blood vessels can also cause nerve damage (diabetic neuropathy) over time, which increases your risk of skin and soft tissue infections. 

  3. High blood sugar levels provide harmful bacteria with an ideal acidic environment in which they can thrive.

  4. Having high blood glucose levels may also limit your immune system’s production of certain types of immune cells – typically white blood cells – that help target and destroy infection-causing micro-organisms (vi), including:

  • Neutrophils

  • Macrophages (as well as killing harmful micro-organisms these also remove dead cells and stimulate the action of other immune system cells)

  • Natural killer cell activity is thought to be lower in people with diabetes compared with those with normal blood sugar (natural killer cells are best known for killing cells infected by viruses)

  • Cytokine production may also be impaired in people with diabetes (cytokines are proteins that allow immune cells to communicate with each other)

Find out more by reading our guide to how your immune system works

Which infections are most common?

If you have diabetes and your blood sugar levels are poorly controlled, you’re at risk of having more than your fair share of the following:
• Foot infections known as diabetic foot ulcers (or diabetic foot), which can, in the worst cases, lead to amputation (find out more by reading our guide to diabetic foot ulcers
• Skin infections, such as fungal yeast infections in skin folds
Urinary tract infections (infections of the bladder, urethra and kidneys)
• Infections of the outer ear (malignant external otitis)
• Fungal infection of the nose and sinuses (zygomycosis, also known as mucormycosis: this is a complication of diabetic ketoacidosis, which is when your body has a severe lack of insulin and produces high levels of blood acids called ketones to burn fat for fuel – diabetic ketoacidosis mostly affects those with type 1 diabetes but can occasionally affect those with type 2 diabetes too)
• Fungal infection of the throat
• Surgical site infections (infections acquired after having surgery) are also more likely in people with diabetes (viii)
Meanwhile, common infections such as flu and pneumonia tend to affect people with uncontrolled diabetes more severely compared with those who have well-managed diabetes or don’t have diabetes. This is why it’s important to get an annual flu jab and the one-off pneumonia vaccine if you have diabetes.

How to lower blood sugar

If you’re living with either type of diabetes and want a healthy immune system, it’s essential to manage your blood sugar levels effectively. Here are some of the things you can do right now to help keep your blood sugar in its target range:

Take your diabetes medication

It’s important to take your medication as prescribed – most people with type 1 diabetes need to take insulin regularly, while some with type 2 diabetes may take tablets that don’t contain insulin (though many eventually need insulin if their tablets stop working effectively). Try to make sure you never miss or stop taking your medicine unless your doctor recommends it. It’s also important to keep going for any check-ups or tests your GP or diabetes team recommends.

Eat healthily

When it comes to your diet aim for a wide range of nutritious foods, including at least five portions of fruit and vegetables and some starchy foods every day (wholemeal carbs are preferable to refined carbs). It’s a good idea to try eating less fat, particularly the saturated kind, and to have two or three portions of lean protein a day. You don’t have to give up sugar altogether, but try to limit it as much as possible. Meanwhile, try not to skip meals – instead have three meals a day at regular intervals (that is, don’t go for too long without eating).

Drink water

Staying hydrated is important if you have diabetes because being dehydrated may affect your blood sugar levels. According to the NHS everyone should drink six to eight cups or glasses of fluid a day (water is ideal as it’s cheap and calorie-free, but other fluids count too, including lower-fat milk, tea, coffee and sugar-free drinks) (ix).

Stay active


Regular exercise can help lower your blood sugar levels plus it can help your body use insulin more effectively (x). Aim for the recommended 150 minutes of moderate activity each week – this should leave you feeling warm and your heart beating faster. Speak to your GP or diabetes nurse if you need advice on exercising with diabetes.

Keep your weight in check

Carrying too much body weight can increase your risk for diabetes and insulin resistance, plus it may also have an effect on your immune system. Try to keep your weight within the normal range – eating healthily and staying active will help you achieve this (for more tips on managing your weight read our guide to the facts on weight loss). 

What are the best supplements for lowering blood sugar?

Certain nutritional supplements may be helpful if you’re trying to keep your blood sugar levels under control, while others may give your immune system some extra support. However if you have diabetes – whether you’re on medication or not – check with your GP before taking these or any other supplements, as there’s a risk your blood sugar could dip too low and put you at risk of a serious complication called hypoglycaemia (hypo).

Find out more about hypos in our guide to diabetes.

Please also note that no supplement should ever be used as an alternative to conventional diabetes medicines or medical care.

If you’re interested in taking supplements, a good one to start with is a quality multivitamin and mineral product. This can help make sure you’re getting all the nutrients your body needs for your general health as well as that of your immune system, particularly if you don’t always eat as healthily as you should.

Find out more about multivitamin supplements, including the variety of products on offer and which one may be suitable for you, by  reading our guide to multivitamins and daily requirements

Other supplements you may want to consider include the following:


One of the oldest remedies used in traditional Chinese medicine, cinnamon is also often recommended by natural therapists for people with type 2 diabetes, as there is some evidence it may help improve blood sugar levels (x).

Alpha lipoic acid

This fatty acid is a powerful antioxidant and some studies suggest it may help control blood sugar levels (xi) as well as improve insulin sensitivity in people with type 2 diabetes (xii). However, if you have diabetes always consult your GP before taking alpha lipoic acid as it may enhance insulin activity.


Some experts believe people who have diabetes also have low magnesium levels (xiii), possibly because diabetes or the medicines used to treat it may cause magnesium deficiency. Elsewhere researchers have discovered magnesium may even help with blood sugar control (xiv).


The curry spice turmeric contains a compound called curcumin that has several potential health benefits, including the ability to reduce blood sugar levels – though to date most studies have been carried out in animals rather than humans, meaning the available evidence isn’t as strong as it could be. Some researchers, however, have studied the effects of taking curcumin in people with diabetic foot ulcers (xv). The results didn’t find any significant improvement in wound healing, though they did suggest that the curcumin supplements improved blood sugar level control.

High-strength fish oils

Omega-3 fatty acids – particularly EPA and DHA, two omega-3s found in oily fish such as salmon, trout, sardines and mackerel, as well as fish oil supplements – are widely considered helpful for general health and wellbeing, including regulating the immune system (xvi). Fish oil supplements are widely available, but vegetarians and vegans can get these beneficial omega-3 fats too by taking supplements that contain omega-3 oils derived from marine algae.


Fenugreek seeds have been used traditionally as a medicine for centuries in some parts of the world (in Ayurvedic medicine, for instance). These days, herbal practitioners recommend fenugreek seeds to people with diabetes, as they may help the body to produce insulin. There’s also some evidence fenugreek seeds may be helpful in controlling type 2 diabetes and reducing insulin resistance, though supporting studies to date are small in scale (xvii). However, don’t take fenugreek if you’re pregnant or breastfeeding.

Vitamin D

Best known for helping the body to absorb calcium, vitamin D is also thought to play an important part in regulating the immune system. Some experts even believe being deficient in vitamin D may be associated with an increased susceptibility to infection (xviii).

Unfortunately vitamin D deficiency is thought to be common in some countries including the UK, which explains why Public Health England advises adults and children over the age of one year old to consider taking a daily supplement containing 10mcg of vitamin D, particularly during autumn and winter (xix). However if your skin is rarely exposed to the sun – if you spend most of your time indoors, for instance, or if your skin is always covered when you’re out and about – you may need to take vitamin D throughout the year. People with dark skin from African, Afro-Caribbean and South Asian backgrounds should consider taking vitamin D all year round too, PHE advises.

The recommended form of vitamin D is vitamin D3 or cholecalciferol, as it’s the natural form of vitamin D that the body makes when it’s exposed to sunlight. Vitamin D3 supplements are available in tablet form, and now you can get them in veggie-friendly drops too. However most vitamin D3 supplements are made from the fat of lamb’s wool, which means they’re unsuitable for vegans. The good news is that vegan vitamin D3 supplements sourced from lichen are now more widely available.

High-strength anthocyanidins

Found in dark-skinned fruits such as blueberries, cranberries, raspberries, blackberries and red grapes – as well as vegetables such as red cabbage, red onions and aubergines –  anthocyanidins and their derivatives anthocyanins are potent antioxidant compounds. These substances may support healthy blood flow, as they help strengthen and repair the walls of blood vessels by protecting collagen in the body (collagen being the structural protein that gives blood vessels their strength).
Anthocyanidins are also available in supplement form (choose a product that combines anthocyanidins with vitamin C, as vitamin C supports the body’s ability to produce collagen).
Living with diabetes means you’re at risk of several complications, including problems with your immune system and a higher vulnerability to infections. Keeping your blood sugar levels healthy and within the target set for you by your GP or diabetes team is the key to preventing and reducing immune system issues, and as this guide shows there are several things you can do to achieve it, including taking your medicines diligently and following a healthy lifestyle. If you need more information about health and wellbeing conditions, we have a range of useful guides in our pharmacy health library


(i) Available online:
(ii) Available online:
(iii) Available online:
(iv) Available online:
(v) Available online:
(vi) Available online:
(vii) Berbudi A et al. Type 2 Diabetes and its Impact on the Immune system. Curr  Diabetes Rev. 2020 May; 16(5):442-449. Available online:
(viii) Martin ET al. Diabetes and Risk of Surgical Site Infection: A Systematic Review and Meta-analysis. lnfect Control Hosp Epidemiol 2016 Jan;37(1):88-99. Available online:
(ix) Available online:
(x) Available online:
(x) Mang. B, Wolters. M, Schmitt. B, et al. Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2. Eur J Clin Invest. 2006;36:340-344. Available online:

Akilen. R, Tsiami. A ,Devendra. D, Robinson. N, et al. Glycated haemoglobin and blood pressure-lowering effect of cinnamon in multi-ethnic Type 2 diabetic patients in the UK: a randomized, placebo-controlled, double-blind clinical trial. Diabet Med. 2010;27(10):1159-1167. Available online:

Pham. AQ, Kourias. H, Pham. DQ. Cinnamon supplementation in patients with type 2 diabetes mellitus. Pharmacotherapy. 2007 Apr;27(4):595-9.Available online:

Kirkham S, Akilen R, Sharma S, Tsiami A. The potential of cinnamon to reduce blood glucose levels in patients with type 2 diabetes and insulin resistance. Diabetes Obs Metab. 2009 Dec;11(12):1100-13. Available online:
(xi) Poh. ZX., Goh KP., A current update on the use of alpha lipoic acid in the management of type 2 diabetes mellitus. Endocr Metab Immune Disord Drug Targets. 2009 Dec;9(4):392-8. Available online:
(xii) Evans JL, Goldfine ID. Alpha-lipoic acid: a multifunctional antioxidant that improves insulin sensitivity in patients with type 2 diabetes. Diabetes Technol ther. Autumn 2000;2(3):401-13. Available online:
(xii) Elamin. A, Tuvemo. T. Magnesium and insulin-dependent diabetes mellitus. Diabetes Res Clin Pract. 1990;10:203-209. available online:

Barbagallow M, Dominguez LJ. Magnesium and type 2 diabetes. World J Diabetes 2015 Aug 25; 6(10):1152-57. Available online:
(xiv) Song. Y, He. K, Levitan. EB. Effects of oral magnesium supplementation on glycaemic control in Type 2 diabetes: a meta-analysis of randomized double-blind controlled trials. Diabet Med. 2006;23:1050-1056. Available online:
(xv) Mokhtari M., Razzaghi R, Momen-Heravi M. The effects of curcumin intake on wound healing and metabolic status in patients with diabetic foot ulcer: A randomized, double-blind, placebo-controlled trial. Phytother Research: PTR (2020) 35(4):2099–107. Available online:
(xvi) Gutierrez S, Svahn SL, Johansson ME. Effects of Omega-3 Fatty Acids on Immune Cells. Int J Mol Sci. 2019 Oct; 20(20): 5028. Available online:
(xvii) Yilmaz Z et al. Supplements for Diabetes Mellitus: A Review of the Literature. Pharm Pract 2017 Dec;30(6):631-638. Available online:

Kassaian N et al. Effect of fenugreek seeds on blood glucose and lipid profiles in type 2 diabetic patients. J Vitam Nutr Res 2009 Jan;79(1):34-9. Available online: .

Gupta A, Gupta R, Lal B. Effect of Trigonella foenum-graecum (fenugreek) seeds on glycaemic control and insulin resistance in type 2 diabetes mellitus: a double blind placebo controlled study. Physicians India 2001 Nov;49:1057-61. Available online:
(xviii) Aranow. C. Vitamin D and the Immune System. J Investig Med. (2011 Aug).59(6): 881–886. Available online:

Hewisom. M. Vitamin D and immune function: an overview. Proc Nutr Soc. (2012 Feb).;71(1):50-6. Available online:
(xix) Available online:


Related Posts


Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.

Our Author - Christine Morgan


Christine Morgan has been a freelance health and wellbeing journalist for almost 20 years, having written for numerous publications including the Daily Mirror, S Magazine, Top Sante, Healthy, Woman & Home, Zest, Allergy, Healthy Times and Pregnancy & Birth; she has also edited several titles such as Women’ Health, Shine’s Real Health & Beauty and All About Health.

View More

Sign up to Nature's Best Newsletter