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What causes type 2 diabetes? The organs behind high blood sugar, and why one fix never works

Updated 3 November 2026 · 16-minute read · Backed by 27 published studies

You cut out the biscuits. You walk after dinner. You take your tablets. And still, every few months, the HbA1c number creeps up. Sound familiar?

It is not because you are doing it wrong. It is because most of the advice you have been given explains only one part of the problem. When we analysed the 70 top-ranking UK web pages for blood sugar searches, not one explained the role of mitochondria, and only four explained glucagon [27]. This guide explains the rest.

Contents

1. What is type 2 diabetes?
2. What causes type 2 diabetes: the nine players
3. Risk factors that speed it up
4. The diabetes cascade: how one failure triggers the next
5. Can type 2 diabetes be reversed?
6. Why single-fix supplements and cures fail
7. How to lower blood sugar across every organ
8. Where GlycoShift fits
9. FAQ
10. References

What is type 2 diabetes?

Diabetes means your blood sugar (glucose) stays higher than your body can safely handle. Doctors diagnose it when your HbA1c, a measure of your average blood sugar over about three months, reaches 48 mmol/mol (6.5%) or more, or your fasting glucose reaches 7.0 mmol/L or more [1]. An HbA1c of 42 to 47 mmol/mol is prediabetes.

Type 1 diabetes is autoimmune: the immune system destroys the cells that make insulin. Type 2 is about 90% of cases and builds slowly, for many reasons. In the UK, 4.6 million people have a diagnosis, about 1.3 million more have type 2 without knowing it, and 6.3 million have prediabetes. That is roughly one adult in five [2].

You have probably heard type 2 described as “your body stops responding to insulin”. That is true, but it is one chapter of a longer story. In 2008 the diabetologist Ralph DeFronzo described eight separate defects working together, which he called the “ominous octet” [3]. Research since then has added the mitochondria, the gut microbiome, sleep and stress hormones. Type 2 diabetes is a network failure.

Quick fact: at least nine players set your blood sugar. Type 2 diabetes begins when several fail together, yet most advice online explains one or two of them.

What causes type 2 diabetes: the nine players

1. Beta cells: why insulin output falls

Beta cells sit in small clusters in the pancreas and release insulin in step with your blood sugar. Insulin tells muscle and fat to take sugar in and tells the liver to stop making it. In type 2 diabetes, beta cells first work overtime to push past insulin resistance, then start to fail. Post-mortem studies found about 63% less beta-cell volume in obese people with type 2 diabetes than in weight-matched people without it [4]. Some cells die. Others are not lost but “forget” how to be beta cells under long-term stress, which suggests part of the loss may be reversible [5].

2. Alpha cells: what glucagon does, and why it stays too high

Alpha cells sit right next to beta cells and release glucagon, the hormone that tells the liver to release sugar. A meal should switch glucagon off. In type 2 diabetes it stays high, even after eating. Researchers Roger Unger and Alan Cherrington argued that diabetes is as much about too much glucagon as too little insulin [6]. Think of insulin as the brake and glucagon as the accelerator. In type 2 diabetes, the brake is weak and the accelerator is stuck down.

3. The liver: why fasting blood sugar is high

Overnight and between meals, your liver keeps you alive by making sugar and releasing its stores. Insulin is supposed to rein that in. In type 2 diabetes the liver ignores insulin but still obeys glucagon, so it keeps pumping sugar out. That is the main reason morning readings run high [3]. Fat stored inside the liver makes it worse. Professor Roy Taylor’s “twin cycle” work shows how liver fat drives insulin resistance in the liver and then spills over to the pancreas [7].

4. Muscle: what insulin resistance really is

After a meal, your muscles soak up most of the sugar that insulin clears from your blood. Insulin resistance in muscle means insulin knocks, but not enough sugar doors (GLUT4 transporters) open. It is often the first measurable change, sometimes decades before diagnosis [3]. There is good news hidden here: working muscles open those doors by a separate route that does not need insulin, which is why a walk after dinner helps even when insulin resistance is strong [8].

5. Fat tissue: when the stores overflow

Healthy fat stores energy safely. When the stores are full, especially deep belly fat, they leak fatty acids into the blood and send out inflammatory signals. Raising fatty acids in healthy volunteers is enough to cause insulin resistance in muscle within hours [9]. Fat that cannot be stored safely ends up where it does harm: in muscle, the liver and the pancreas. Scientists call this lipotoxicity, and it explains why two people of the same weight can carry very different risk.

6. Mitochondria: the missing link in insulin resistance

Mitochondria are the engines inside your cells that burn sugar and fat for energy. In muscle from people with type 2 diabetes, they are smaller and less active [10]. In young, lean adults whose parents have type 2 diabetes, muscle mitochondria were already about 30% less active, and insulin resistance was already there, years before blood sugar rose [11]. When the engines cannot burn fat fast enough, fat fragments build up inside the cell and jam insulin’s signal [12]. Beta cells rely on their mitochondria to sense sugar and release insulin, so the same weakness hits the pancreas too [12]. Mitochondria are not one more box on the list. They run through all the others.

7. The gut: GLP-1 and the incretin effect

Sugar you swallow triggers a much bigger insulin response than the same sugar given into a vein. Gut hormones, mainly GLP-1 and GIP, cause this “incretin effect”: they prime the beta cells and calm glucagon. In type 2 diabetes the incretin effect is much weaker [13]. The gut’s bacteria change too, with fewer of the butyrate-producing species [14]. The success of GLP-1 medicines shows how much this one signal matters.

8. The kidneys: what SGLT2 does

Every day your kidneys filter about 180 g of sugar and pull almost all of it back into the blood through a transporter called SGLT2. In type 2 diabetes, the kidneys turn up their capacity to reclaim sugar, holding on to the very thing your body is struggling to clear [15]. SGLT2-inhibitor medicines work by switching this off.

9. The brain: appetite, sleep and stress

The hypothalamus reads insulin, leptin and nutrient signals to set your appetite, your energy use and how much sugar the liver releases. A landmark review in Nature proposed that blood sugar is controlled by a partnership between the brain and the pancreas, and that type 2 diabetes involves a failure of both [16]. When the brain’s fullness signals weaken, you eat more and every other organ takes on more load.

Risk factors that speed it up

• Long-term inflammation. Fat tissue in obesity makes TNF-alpha, a signal that directly causes insulin resistance [17].
• Short sleep. Four hours a night for six nights pushed healthy young men’s glucose tolerance into the range seen in early diabetes [18].
• Stress hormones. Cortisol makes the liver release sugar and blocks insulin. In the CATALYST study, 23.8% of people whose type 2 diabetes stayed high despite several medicines had too much cortisol [19].
• Genes. The TCF7L2 gene is the strongest common genetic risk factor for type 2 diabetes, and it mainly affects beta cells [20]. Genes load the gun; lifestyle pulls the trigger.
• Time. Beta-cell function keeps falling after diagnosis, which is why the UK Prospective Diabetes Study found most people needed more treatment year after year [21].

The diabetes cascade: how one failure triggers the next

None of these failures stays in its own lane. This is how the dominoes usually fall.

1. Brain to fat. Appetite, short sleep and stress push energy in beyond what fat tissue can safely store.
2. Fat to mitochondria. Full fat stores spill fatty acids into the blood and overload the engines in muscle and liver [9][12].
3. Mitochondria to muscle. Unburned fat fragments jam insulin’s signal, so muscle takes up less sugar [11][12].
4. Muscle to pancreas. Beta cells pump out more insulin to compensate. For years this hides the problem: your blood sugar looks normal while your insulin runs high.
5. Pancreas to liver. Overworked, fat-loaded beta cells fail or lose their identity [4][5], while alpha cells keep releasing glucagon [6]. Less insulin plus more glucagon tells the liver to keep making sugar.
6. Liver back to the brain. The liver releases sugar day and night [3][7]. High insulin and sugar dull the brain’s fullness signals, and the loop starts again [16].

Then comes the vicious twist. High sugar and high fat directly damage the beta cells and mitochondria that were still holding the line, so the system fails faster the longer it runs [3][12]. Meanwhile the gut’s incretin effect fades [13] and the kidneys reclaim more sugar [15].

Quick fact: in young, lean adults with a family history of type 2 diabetes, muscle mitochondria were already about 30% less active, years before blood sugar rose [11].

Can type 2 diabetes be reversed?

For many people, yes. The cascade runs in both directions. In the Counterpoint study, an eight-week low-calorie diet cleared fat from the liver and pancreas and beta cells started working normally again [22]. In the larger DiRECT trial, almost half the people on a structured weight-loss programme were in remission at one year [23]. Five-year follow-up showed some people stayed in remission that long [26]. Doctors call it remission rather than a cure, because the cascade can restart if weight returns.

The lesson is not “just lose weight”. It is that taking pressure off several organs at once lets the network recover.

Why single-fix supplements and cures fail

If type 2 diabetes involves nine players, a product aimed at one of them cannot be “the” answer. Yet a lot of the market sells exactly that: one spice, one mineral, one capsule that promises to melt away diabetes.

Even prescription medicines show the limit of the single-target approach. In the ADOPT trial, after five years on one medicine, 15% of people on rosiglitazone, 21% on metformin and 34% on glibenclamide had lost control of their blood sugar [24]. That is why guidelines add medicines over time, and why NICE now starts most people on two at once, metformin plus an SGLT2 inhibitor [25].

Our own research found the same blind spot online. Across 70 top-ranking UK pages, the supplement and natural-remedy results were the least likely to explain more than one organ, and most of the single-answer pages sat there [27].

Four signs of a single-fix promise:

• It names one cause (“it’s all about sugar”) and one cure.
• It promises to reverse or cure diabetes with a capsule and never mentions food, movement, sleep or weight.
• It cannot tell you which organ each ingredient works on, or shows no human trials.
• It hides its doses behind a “proprietary blend”.

How to lower blood sugar across every organ

If the problem is a network, the answer is a set of levers that each reach several organs. Here they are, with the organs they reach.

Lever	Organs it reaches	What the evidence shows
Losing liver and belly fat	Liver, beta cells, fat tissue, muscle	Clearing liver and pancreas fat restored insulin release; 46% remission at one year in DiRECT [22][23]
Walking after meals and strength training	Muscle, mitochondria, liver	Working muscle takes in sugar without insulin; training builds new mitochondria [8]
Fibre-rich, lower-GI meals	Gut, liver, pancreas	Slows the sugar rush and feeds butyrate-producing bacteria [14]
Seven to nine hours of sleep	Brain, muscle, pancreas	Short sleep alone impairs glucose tolerance [18]
Managing stress	Brain, liver (through cortisol)	Cortisol raises liver sugar output and blocks insulin [19]
Medicines	Each class targets one or two organs	Combinations hold up better over time [24][25]. See our guide to metformin, berberine and the alternatives
Researched plant compounds and nutrients	Depends on the compound	The strongest act on several organs at once, berberine above all

The rule of thumb is simple: match the number of levers to the number of failures. One habit, one tablet or one capsule will always leave most of the network untouched.

Where GlycoShift fits

We built GlycoShift around this network, not around one ingredient. It supports natural blood sugar balance* with 11 researched ingredients aimed at the mitochondria, insulin sensitivity, the liver and the pancreas, led by a 300 mg berberine phytosome. Every dose is on the label. We break down what each ingredient does, organ by organ, in part two of this series.

The cascade took years to build, so give your body time to turn it round. The 90-Day Plan is three bottles for £73.50: 82p a day and £15 less than buying them one at a time. The offer price ends on 31 December 2026.

Start your 90 days with GlycoShift

*Chromium contributes to the maintenance of normal blood glucose levels. Food supplements should not replace a varied, balanced diet and a healthy lifestyle.

FAQ

What causes type 2 diabetes?

Several organs failing together. Muscle, liver and fat become resistant to insulin, beta cells in the pancreas tire, alpha cells release too much glucagon, and the mitochondria, gut, kidneys and brain all add to the load [3][6][12].

Is type 2 diabetes just insulin resistance?

No. Insulin resistance usually comes first, but diabetes only develops when beta cells can no longer keep up, while glucagon stays high and the liver keeps making sugar [3][4][6].

What does glucagon do in type 2 diabetes?

Glucagon from the pancreas’s alpha cells tells the liver to release sugar. In type 2 diabetes it stays too high, even after meals, which pushes blood sugar up alongside low insulin [6].

What role do mitochondria play in insulin resistance?

When mitochondria cannot burn fat fast enough, fat fragments build up in muscle and liver and block insulin’s signal. Beta cells also need healthy mitochondria to release insulin [11][12].

Can type 2 diabetes be reversed?

For many people it can go into remission. In DiRECT, 46% of participants were in remission at one year after a structured weight-loss programme, as fat cleared from the liver and pancreas [22][23].

Why don’t single supplements fix blood sugar?

Because type 2 diabetes involves several organs failing together. Even single prescription medicines lose control over time in many people [24], which is why combined approaches work best.

References

1. American Diabetes Association Professional Practice Committee. 2. Diagnosis and classification of diabetes: Standards of Care in Diabetes 2026. Diabetes Care. 2026;49(Suppl 1).
2. Diabetes UK. Diabetes and prediabetes figures, March 2025: 4.6 million diagnosed, 1.3 million undiagnosed, 6.3 million with non-diabetic hyperglycaemia.
3. DeFronzo RA. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus. Diabetes. 2009;58(4):773-795. doi:10.2337/db09-9028
4. Butler AE, Janson J, Bonner-Weir S, et al. Beta-cell deficit and increased beta-cell apoptosis in humans with type 2 diabetes. Diabetes. 2003;52(1):102-110. doi:10.2337/diabetes.52.1.102
5. Talchai C, Xuan S, Lin HV, Sussel L, Accili D. Pancreatic β cell dedifferentiation as a mechanism of diabetic β cell failure. Cell. 2012;150(6):1223-1234. doi:10.1016/j.cell.2012.07.029
6. Unger RH, Cherrington AD. Glucagonocentric restructuring of diabetes: a pathophysiologic and therapeutic makeover. J Clin Invest. 2012;122(1):4-12. doi:10.1172/JCI60016
7. Taylor R. Pathogenesis of type 2 diabetes: tracing the reverse route from cure to cause. Diabetologia. 2008;51(10):1781-1789. doi:10.1007/s00125-008-1116-7
8. Richter EA, Hargreaves M. Exercise, GLUT4, and skeletal muscle glucose uptake. Physiol Rev. 2013;93(3):993-1017. doi:10.1152/physrev.00038.2012
9. Roden M, Price TB, Perseghin G, et al. Mechanism of free fatty acid-induced insulin resistance in humans. J Clin Invest. 1996;97(12):2859-2865. doi:10.1172/JCI118742
10. Kelley DE, He J, Menshikova EV, Ritov VB. Dysfunction of mitochondria in human skeletal muscle in type 2 diabetes. Diabetes. 2002;51(10):2944-2950. doi:10.2337/diabetes.51.10.2944
11. Petersen KF, Dufour S, Befroy D, Garcia R, Shulman GI. Impaired mitochondrial activity in the insulin-resistant offspring of patients with type 2 diabetes. N Engl J Med. 2004;350(7):664-671. doi:10.1056/NEJMoa031314
12. Lowell BB, Shulman GI. Mitochondrial dysfunction and type 2 diabetes. Science. 2005;307(5708):384-387. doi:10.1126/science.1104343
13. Nauck M, Stöckmann F, Ebert R, Creutzfeldt W. Reduced incretin effect in type 2 (non-insulin-dependent) diabetes. Diabetologia. 1986;29(1):46-52. doi:10.1007/BF02427280
14. Qin J, Li Y, Cai Z, et al. A metagenome-wide association study of gut microbiota in type 2 diabetes. Nature. 2012;490(7418):55-60. doi:10.1038/nature11450
15. DeFronzo RA, Davidson JA, Del Prato S. The role of the kidneys in glucose homeostasis: a new path towards normalizing glycaemia. Diabetes Obes Metab. 2012;14(1):5-14. doi:10.1111/j.1463-1326.2011.01511.x
16. Schwartz MW, Seeley RJ, Tschöp MH, et al. Cooperation between brain and islet in glucose homeostasis and diabetes. Nature. 2013;503(7474):59-66. doi:10.1038/nature12709
17. Hotamisligil GS, Shargill NS, Spiegelman BM. Adipose expression of tumor necrosis factor-alpha: direct role in obesity-linked insulin resistance. Science. 1993;259(5091):87-91. doi:10.1126/science.7678183
18. Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-1439. doi:10.1016/S0140-6736(99)01376-8
19. Buse JB, Kahn SE, Aroda VR, et al. Prevalence of hypercortisolism in difficult-to-control type 2 diabetes (CATALYST). Diabetes Care. 2025. doi:10.2337/dc24-2841
20. Grant SFA, Thorleifsson G, Reynisdottir I, et al. Variant of transcription factor 7-like 2 (TCF7L2) gene confers risk of type 2 diabetes. Nat Genet. 2006;38(3):320-323. doi:10.1038/ng1732
21. Turner RC, Cull CA, Frighi V, Holman RR. Glycemic control with diet, sulfonylurea, metformin, or insulin in patients with type 2 diabetes mellitus: progressive requirement for multiple therapies (UKPDS 49). JAMA. 1999;281(21):2005-2012. doi:10.1001/jama.281.21.2005
22. Lim EL, Hollingsworth KG, Aribisala BS, et al. Reversal of type 2 diabetes: normalisation of beta cell function in association with decreased pancreas and liver triacylglycerol. Diabetologia. 2011;54(10):2506-2514. doi:10.1007/s00125-011-2204-7
23. Lean MEJ, Leslie WS, Barnes AC, et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet. 2018;391(10120):541-551. doi:10.1016/S0140-6736(17)33102-1
24. Kahn SE, Haffner SM, Heise MA, et al. Glycemic durability of rosiglitazone, metformin, or glyburide monotherapy (ADOPT). N Engl J Med. 2006;355(23):2427-2443. doi:10.1056/NEJMoa066224
25. NICE. Type 2 diabetes in adults: management (NG28). Updated February 2026. nice.org.uk/guidance/ng28
26. Diabetes UK. Weight loss can put type 2 diabetes into remission for at least five years, DiRECT study reveals. February 2024.
27. Brittica. We analysed 70 top-ranking blood sugar pages. Not one explained mitochondria. November 2026. brittica.co.uk