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1 November 2022

Definitive Guide for Type 2 Diabetes


The purpose of this guide is to help answer any questions you may have about Type 2 Diabetes particularly how it affects adults. While I hope it is informative and useful, if you have concerns about your own health, please use it as an adjunct to, and not a replacement for, seeking medical advice.

Lancet Glucose

Dr Katie BlogWritten by Dr Katie Stephens, GP

Dr Katie graduated from the University of Manchester in 2007 (MBChB) and completed her GP training in the West Midlands in 2012 (MRCGP). 

What is Type 2 Diabetes?

Type 2 Diabetes (T2DM) is a disease of raised blood sugar levels. Normally, if the blood sugar gets too high, it is brought back down to a healthy range by a hormone called insulin. In T2DM, insulin either stops working properly, or there isn’t enough of it. Or sometimes, both. The result is that sugar levels stay high. This can cause serious damage both in the short term, and the long term.

In the UK, someone is diagnosed with diabetes every 2 minutes, with an estimated 4.7 million people now affected. Somewhat surprisingly, over half of the people diagnosed don’t have symptoms at the time, and around a million people in the UK are thought to have it without knowing. Additionally, the NHS spends £19,000 a minute on diabetes, and every hour someone has an amputation because of it.

How are sugar levels normally controlled?

The cells in our body use sugar (glucose) as an energy source to help them function. Usually, the amount of glucose being carried around in our bloodstream can vary by a reasonable amount within a ‘normal range’. It is affected by factors such as how long ago someone has eaten, or how active they have been.

When the sugar level fluctuates above or below where it should be, this is sensed by our pancreas, which then responds by releasing a hormone to bring the level back towards normal. The pancreas is an internal organ, roughly the size of your hand, located in the top left of your abdomen, tucked just below your stomach.

Excess sugar in our body is stored in the liver, where it is clumped together into larger packages called glycogen.

Let’s look at an example of how the pancreas works when the sugar levels drop: imagine you have just run 5k. The muscles in your legs will have used up lots of the available sugar in the blood stream to give them energy to run that far. This leads to a drop in the blood sugar level. The pancreas sees this and releases a hormone called glucagon. Glucagon then travels around the body, including going to the liver. It tells the liver to release sugar back into the blood stream, bringing the blood sugar level back up to normal. A bit of extra info: the name for this process, where the liver breaks apart glycogen to release glucose into the blood, is called gylocengolysis (lysis meaning ‘to break apart’).

Glucagon also turns amino acids (the smaller building blocks of protein) into glucose, and breaks down fat into smaller chunks for cells to use as energy. The net effect is a boost up to our sugar levels.

Conversely, if we have just eaten (or sometimes even if we have just seen or smelled some yummy food), our pancreas secretes the hormone insulin. This acts in a few ways to lower our blood glucose levels:

  • Telling our cells to open up and pull in some of the glucose from the bloodstream.
  • Telling our liver to store more glucose (as glycogen).
  • Using glucose to make and store fats and cholesterol

If there isn’t enough insulin traveling round the body, or if the cells it normally affects become less sensitive to it (insulin resistance), it follows on that the sugar levels don’t drop as they should, and instead stay elevated.

What’s the difference between Type 1 and Type 2 Diabetes?

Type 1 Diabetes (T1DM) happens when the pancreas becomes so badly damaged that it stops making insulin altogether. This typically is due to the body’s immune system mistakenly attacking the pancreas (an example of an auto-immune disease). People with Type 1 Diabetes tend to have symptoms younger and get diagnosed as children or young adults. The old name for this is Insulin-Dependent Diabetes Mellitus, or IDDM.

With Type 2 Diabetes, as described above, there is still insulin in the body, just either not enough of it, or what is present does not have the desired effect as the body stops responding normally to it. It tends to come on later in adult life and is linked to being overweight (although with the trend towards more young people being overweight, people are getting diagnosed younger and younger these days). The old name for T2DM is Non-Insulin Dependent Diabetes Mellitus, or NIDDM. This can be a bit misleading, however, as there are some people with Type 2 Diabetes who do need insulin (just not everyone).

What is Pre-Diabetes?

Pre-Diabetes is the diagnosis used for people whose blood sugar levels are higher than they should be, but not quite high enough to be diagnosed as Diabetic. It is worth identifying these people as they have a risk of progressing to develop Diabetes.

Usually, Pre-Diabetes is discovered when someone is tested for Diabetes using the HbA1c test. This test gives an average sugar level reading taking into account what the sugars have been for the previous 3 months.

Are there other types of diabetes?

Gestational Diabetes

When pregnant women have Diabetes only during pregnancy and resolving soon after delivery, it is known as Gestational Diabetes. Women who have had Gestational Diabetes are known to be at increased risk of progressing to have a longer lasting type of Diabetes later in life. For those who do, the vast majority will have , although some may develop T1DM.

The other Diabetes:

You may wonder why we sometimes use the term ‘Diabetes Mellitus’. This is because there is a whole different type of Diabetes that has nothing to do with blood sugars at all: Diabetes Insipidus. This is a rare condition that involves too much urine being made, due to a malfunctioning of either the brain or the kidneys. Now you know why we differentiate the blood sugar Diabetes from this type with the extra word ‘Mellitus’ (Latin for ‘sweet’). From here on out though, I will not reference Diabetes Insipidus again so any time I use the word ‘Diabetes’, I am referring to Diabetes Mellitus, specifically Type 2.

diagnosed with diabetes every 2 minutes

Risk Factors

The biggest risk factor for developing T2DM is carrying extra fat. In fact, many would argue that carrying extra fat isn’t a risk factor for developing diabetes but is actually the direct cause. How this happens is somewhat complex but I have summarised two of the main ideas:

  1. The fat we carry affects the way our body responds to insulin. When we have more fat on us, our body becomes less sensitive to insulin (insulin resistance). Remember, insulin lowers our blood sugar. If our body isn’t listening to the insulin, the blood sugar then stays high.
  2. When the usual places that fat live (think ‘love handles’ or other areas just under the skin) become ‘full’, fat is then stored in and around the internal organs, including the pancreas and liver. This can lead to inflammation and damage here, affecting both the production of insulin and the body’s sensitivity to it.

With the underlying cause being excess fat itself rather than just being over a certain weight, using the waist:hip ratio gives a better predictor of risk than a BMI (Body Mass Index, or height:weight ratio). This is because the latter doesn’t take into account muscle mass and may both overestimate risk in someone with a muscular build and raised BMI, and underestimate risk in someone with a normal BMI who is carrying less muscle and more fat than is healthy.

Having a family history of Diabetes also increases your risk, as does a history yourself of Gestational Diabetes or Pre-Diabetes.

What are the symptoms of type 2 diabetes?

Two of the main symptoms of diabetes are:

  1. Weeing more (polyuria)
  2. Excessive thirst (polydipsia)

Other symptoms include:

  1. Recurrent infections
  2. Fatigue

Symptoms of Type 2 DM Emergencies

Things can get serious quickly if the blood sugar rises very high or very low.

  1. HHS (Hyperosmolar Hyperglycaemic State)

In T2DM, an excessively high sugar level can cause a condition called HHS, which stands for Hyperosmolar Hyperglycaemic State. Symptoms of this include:

  1. Above-baseline levels of excessive thirst
  2. Above-baseline levels of urination
  3. Confusion
  4. Nausea

This might happen if someone forgets to take their medication or if their sugar levels rise above normal due to an infection.

HHS are rare, but it is a serious medical emergency when it does happen as it has a high mortality rate. HHS will normally take days to develop rather than hours. If someone with you has HHS, take them to A&E or ring 999 immediately. If you are unsure whether someone has HHS, but you think their blood sugar levels are high and they look poorly (and they don’t have T1DM), ring their GP or 111 immediately.

  1. Hypoglycaemia (Hypo)

This is when the blood sugar level falls too low. This can be due to issues with the following:

  1. Medication types and amounts
  2. How much is eaten
  3. Exercise intensity and duration
  4. Drinking alcohol

Usually, a cut-off of less than 4 mmol/L is used to diagnose hypoglycaemia – also known as having ‘a hypo’.

Symptoms of Hypoglycaemia (Hypo)

  1. Shakes
  2. Nausea
  3. Dizziness
  4. Sweating
  5. Confusion
  6. Fatigue
  7. Drowsiness

If you are with someone you think is having a hypo, get them something that has sugar it in to eat or drink quickly and stay with them, making sure they feel better soon. If they faint, ring 999. For more details, check out our page from St John Ambulance, or




The best test for investigating possible T2DM for most people is the HbA1c. This is a measure of how much haemoglobin has sugar attached to it (glycated haemoglobin). Haemoglobin is the part inside the red blood cell that carries oxygen. We all have some sugary haemoglobin, but knowing how much there is tells us what the sugar levels in the blood are like generally.

There are certain instances where this test may not be appropriate. Other conditions that affect red blood cell or haemoglobin levels may interfere with the interpretation. Examples include:

  • Age <18 years old
  • Pregnancy or within 2 months of being pregnant
  • If symptoms have lasted <2 months
  • Haemoglobinopathies (eg thalassaemia), anaemia
  • Having had a recent blood transfusion

The HbA1c is one of the Home Health Tests that we offer at Kinetik. A normal range is 20 – 41 mmol/mol. 42 – 47 Mmol/mol is usually considered Pre-Diabetic, and 48 mmol/mol (or, in ‘old money’, 6.5%) is usually used as the cut off for diagnosing Diabetes.

Blood sugar level

The advantage of this test is it doesn’t rely on a normal haemoglobin, so it can be useful if one of the above conditions applies. The disadvantage is that it really only gives a snapshot picture of what the blood sugar is in that very second that the test is taken. As sugar levels can go up and down, it can be falsely reassuring if the sugar level is tested in a moment when it is normal, even if that person actually has diabetes. It can also be falsely worrying as other conditions such as infection and trauma can raise sugar levels temporarily.

According to NICE, the National Institute for Health and Clinical Excellence, we should be concerned about possible Type 2 diabetes when testing blood sugar levels in the following instances:

  • Fasting level of 7.0 mmol/L or more.

Random level of 11.1 mmol/L or more, in the presence of symptoms or signs of diabetes.


Typically, someone is diagnosed with Type 2 DM by their NHS GP, based on symptoms and blood results.

NICE says that if an adult has an abnormal HbA1c or fasting blood sugar, and has symptoms of diabetes, a single result can be used to diagnose this, while it recognises that repeat testing to confirm the diagnosis is sensible.

If they do not have symptoms, NICE advises repeat testing and monitoring.

You may be wondering how we can know if someone with symptoms of diabetes and abnormal test results has Type 2 DM and not Type 1. If so, good question! Generally, if someone is an adult who is overweight and has had their symptoms come on gradually, it is more likely that they have Type 2 DM. Nine out of ten people with Diabetes have Type 2. A history that would make the GP consider Type 1 DM may include things like symptoms starting at a young age, being depending on insulin from the get-go, symptoms progressing quickly, and a medical condition that is typically only linked with Type 1 called ketoacidosis.

If there is doubt about the type of Diabetes, the GP may involve a specialist doctor (Endocrinologist).

If the person in question is a child or young person, NICE advises that they are seen that day in the hospital to be assessed/diagnosed and have treatment started.


With T2DM being linked directly to carrying extra body fat, it is no surprise then that the first step to managing it is lifestyle changes that address this.



  • Wholegrain carb options (wholegrain bread, wholewheat pasta, brown rice) instead of white.
  • At least 5 portions of fruit and vegetables daily
  • Unsweetened, low-fat dairy products
  • Oily fish at least once or twice per week
  • Pulses (beans, lentils, chickpeas, peas)


  • High sugar drinks and foods.
  • Minimise foods high in salt and trans-fats (bad fats e.g., anything fried).
  • Processed food marketed specifically for people with diabetes.

Have regular meal patterns (for people treated with medication that can cause a hypo, this can reduce the chance of that happening).

Avoid excess energy intake (taking in more calories than you spend). Having a low-calorie diet (provided it is safe for you, of course!) can aid weight loss and improve outcomes for people with diabetes.

  • Exercise
    • Exercise can lead to weight loss which can not only prevent people from developing T2DM as well as improve outcomes for someone who has been diagnosed, but can even go so far as to completely reverse Type 2 DM.
  • Alcohol
    • Alcohol affects how your body manages blood sugar levels and can make getting a hypo more likely. While Diabetes doesn’t need to stop you from enjoying a drink, it’s important to be wise about what this looks like for you. For some people, this might mean having a snack before and after drinking, and wearing a bracelet or other identifier to show that they have Diabetes. For more information, please read Diabetes UK’s fantastic resource here.
  • Smoking
    • You may be surprised to learn that smoking actually increases blood sugar levels, by making blood cells less responsive to insulin. It can therefore both increase the risk of someone getting Diabetes and also make existing Diabetes worse. Smoking also increases the risk of developing other conditions linked to Diabetes, such as strokes, heart attacks and kidney failure.
  • Recreational Drug Use
    • The main thing to be aware of here is that using recreational drugs when you have Diabetes may affect your ability to keep your blood sugar levels in a safe range. Diabetes UK, while advising against recreational drug use, recommends that you ensure that you are with a friend who knows both about your Diabetes and how to treat a Diabetic Emergency, should you decide to use them.


The number of different types of anti-Diabetic medication on offer for T2DM has increased significantly in the last few years. To simplify things, I’ve picked out some of the most commonly-used options here. It can get a little confusing trying to remember which drug does what, so hopefully this will be a handy guide.

  • Metformin (e.g., Glucophage)
    • Metformin works by amplifying the effects of the body’s insulin, reducing the formation of new glucose in the liver, and getting glucose out of the bloodstream and into cells where it can be used up.
  • Sulfonylureas (e.g., Gliclazide, Glimepiride)
    • These are sometimes added in to be used with Metformin, or potentially on their own. They work by stimulating the pancreas to release more insulin. Because of this, they can cause a hypoglycaemic attack. They can also cause weight gain.
  • DDP-4 Inhibitors (e.g., Alogliptin, Sitagliptin)
    • These increase insulin secretion and reduce secretion of insulin’s ‘opposite’ hormone, glucagon. They don’t seem to cause either hypo’s or weight gain as often as sulfonylureas.
  • SGLT2 Inhibitors (e.g., Canagliflozin, Dapagliflozin)
    • Makes the kidneys secrete more glucose into the urine, meaning there is less in the bloodstream. However, these have rarely been linked to a serious condition known as Diabetic Ketoacidosis.
  • Insulin
    • Insulin is always injected and cannot be taken in tablet form. There are many different types of insulin, some short-acting, others longer-acting, and some a combination of the two.

Read: Managing Type 2 Diabetes – Diet, Exercise & Medication


We discussed the acute emergency situations that can arise when a blood sugar level is dangerously high or low in the Symptoms section. However, Diabetes also poses risks to the body through damage done slowly over time, even with less severely-raised sugar levels. This damage tends to come about somewhat indirectly, through the effect of the raised sugar level on blood vessels themselves. We can categorize the complications from Diabetes in terms of the size of the blood vessels affected.

Microvascular Complications

When smaller blood vessels are damaged in Diabetes, it can cause problems with the eyes, the kidneys, and the nerves. The risk of the damage happening is linked to both how high the blood sugars get, and how long someone has Diabetes for.

Eye Damage (Diabetic Retinopathy)

It is concerning to know that the eyes may start to be damaged up to 7 years before someone is diagnosed with T2DM, and Diabetic Retinopathy accounts for 10,000 new cases of blindness in the US each year.

When eye damage is found early enough, it can be treated before it gets severe. This is why it is so important to attend regular eye screening appointments, and also to get medical attention in between appointments if you notice any changes to your vision. The NHS arranges regular eye screening for people who have Diabetes.

Kidney Damage (Diabetic Nephropathy)

Damage to the kidneys reduces their ability to filter the blood properly. Some components of the blood, like proteins, should stay in the bloodstream. However, damaged kidneys tend to leak this protein out into the urine. Testing for protein in the urine is therefore one of the best ways of assessing how well the kidneys are working.

If there is protein found, new medication may be started to try to protect the kidneys from further damage as much as possible, as well as checking for other risks to the kidneys such as raised blood pressure.

Other medication may need to be reviewed, to make sure it is still safe to keep taking the same doses. (If the kidneys are the medication’s Exit Door from the body, and the foot traffic moving through is slow, the medication can accumulate, which can cause even bigger problems.)

Nerve Damage (Diabetic Neuropathy)

This is estimated to affect up to half of all people with Diabetes. Typically, the feet and or hands are involved (in which case it is termed a peripheral neuropathy). Symptoms may vary but often include experiencing numbness/loss of feeling, pins and needles or burning/stabbing pain. It often starts just at night but can then progress to become more persistent.

When the nerves affected are more central in our body, this is termed an autonomic neuropathy. There are loads of different symptoms that this can cause, but just a couple of examples include erectile dysfunction and postural hypotension, which is when the blood pressure drops when someone stands, causing dizziness.

Macrovascular Complications

These tend to occur as a result of atherosclerosis – the process by which the inner aspects of artery walls become damaged and can clog up with fatty plaques, narrowing the amount of blood getting through. If these clogs burst, they can block off the whole vessel, causing whatever is downstream to go without the essential oxygen and nutrients blood would usually carry to it (infarction).

Heart Attacks (Coronary Artery Disease)

People with T2DM are 2.5 times more likely than non-Diabetics to have a heart attack and develop heart failure. Each day in the UK, diabetes causes about 75 heart attacks and 275 cases of heart failure, on average (27,000 and 100,000 respectively, per year).

Strokes (CVA, Cerebrovascular Accident)

Diabetes causes approximately one in five strokes, equivalent to over 35,600 per year in the UK. People in the first 5 years of being diagnosed with T2DM are twice as likely as non-Diabetics to have a stroke.

Peripheral Arterial Disease

When the arteries in the legs get damaged by Diabetes and atherosclerosis, it can cause multiple problems, including a condition known as Intermittent Claudication. This is where very painful cramps can occur on walking, which can limit mobility.

It can also cause problems with one’s feet. A poor arterial supply can impact how well the foot can heal after trauma. Combine this with the risk of not being aware of an injury due to numbness from nerve damage, and it is no surprise that people with Diabetes are at risk of quite serious foot ulcers and long-term problems here. A non-healing ulcer or deep bone infection (osteomyelitis) can sometimes even lead to the need to amputate.


Once someone is diagnosed with T2DM, aside from discussing the above important points with regards to lifestyle advice, treatment options and risk of complications, there is usually a plan put in place for monitoring. The main objectives for monitoring are:

1.     Monitoring for risk of complications

This would include regular eye checks, foot checks and kidney health checks, all done through the NHS.

2.     Monitoring sugar levels

As many of the complications are more likely with higher sugar levels, it is sensible to agree to set a treatment target to aim towards, in order to reduce the chance of these complications occurring. NICE recommends a target HbA1c of 48 mmol/mol for people who aren’t at risk of getting a hypo – i.e. if they are managing their Diabetes through lifestyle changes alone, or with only using metformin and no other medication. For these people, and also for those who aren’t pregnant or planning a pregnancy, NICE doesn’t recommend routinely monitoring snapshot blood sugar levels. The HbA1c is the superior test here.

If someone is taking other medication that can cause hypo’s, NICE advises a target of 53 mmol/mol. The advantage of a less-strict target here means that someone is less likely to try to have super-tight sugar control – something that is often associated with getting a hypo.

NICE also recommends checking the HbA1c every 3 – 6 months to start with, until it is stable and the treatment hasn’t changed, then swapping to every 6 months.

3.     Other Risk Factors for Complications

Diabetes is not the only condition that can lead to some of the above complications. High blood pressure, raised cholesterol and smoking can all be linked with the Macrovascular Complications, as well as damage to the kidneys and sexual function. Hypertension can also cause eye damage. For this reason, it is worth assessing the smoking status, blood pressure and cholesterol levels of someone with Diabetes regularly.

If someone with Diabetes is found to have high blood pressure, because of the significant damage that can occur with both, usually more aggressive treatment is used to get the blood pressure to a lower target than someone without Diabetes.

4.     Damage from medication

While generally the medication used to treat Diabetes should do far more good than harm, it is generally sensible to check routinely that all is as it should be. For instance, there are reports that high doses of metformin taken long-term may reduce the absorption of Vitamin B12, so it would be sensible to check B12 levels periodically for someone who might be at risk of B12 deficiency (e.g., someone with a vegan diet).

We also know that, if the kidneys aren’t working well, someone could develop a serious condition called lactic acidosis while taking metformin. For this reason, kidney function is usually monitored prior to starting this medication as well as regularly afterward.


Type 2 Diabetes is a serious condition affecting millions of people in the UK, which poses real threats both in terms of emergency situations and long term damage in the body. There are ways of minimising harm through regular monitoring and treatment, and potentially even recovering from Diabetes through sustained lifestyle changes and weight loss.

If you think you might have Diabetes, please do something about it. While it might be tempting to just monitor symptoms, the best thing to do is test for it and speak to your GP. It may be nothing, but if you do have Diabetes, the sooner you are diagnosed, the sooner you can have your risk of harm reduced.

For more info, please visit Diabetes UK, which has some fantastic resources that explore all the ins and outs of living with Diabetes in great detail, or speak to your NHS GP.


HypoHypoglycaemic attack – episode of dangerously low blood sugar (typically <4 mmol/L)
InsulinHormone secreted by the pancreas which lowers blood sugar levels
NICENational Institute for health and Clinical Excellence
PancreasOrgan in the body that controls blood sugar levels
T1DMType 1 Diabetes Mellitus
T2DMType 2 Diabetes Mellitus

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