I eat healthy but have suboptimal glucose levels. Why?

I eat healthy but have suboptimal glucose levels. Why?

Many patients I see have perfectly healthy diets but unfortunately suffer with suboptimal glucose levels. This can be frustrating for the patient. Especially as they are doing their best to control their diabetes but to no avail.

When I see these patients in clinic they can be quite downbeat. It seems regardless of the dietary changes they make the glucose levels remain elevated.

This has come up quite frequently recently and so I thought I’d write about some of the reason you may this.

I will be referring to both type 1 and type 2 diabetes throughout so just pick the content relevant to you.

1. Inappropriate Medication

Type 1 diabetes

Type 1 diabetes is an autoimmune disease. These patients produce none of their own insulin, the hormone responsible for controlling blood glucose levels. Without insulin, glucose levels rise unopposed until a tipping point is reached, which if left untreated, becomes fatal.

They therefore need to inject insulin several times per day to compensate for their lack of it. How much insulin they require is very individual.

If the insulin is incorrect blood glucose levels may either drop too low or climb too high. Dietary changes will unlikely help this.

Your background or long acting insulin is not effected by food. Therefore, if you wake up with large swings in your levels from the night before it is likely there is a mismatch in insulin given to insulin requirement.

Your rapid acting insulin should match your carbohydrate intake. If there is an imbalance between the two, glucose levels will remain out of target. It doesn’t matter if you eat healthy or not.

Type 2 diabetes

Type 2 diabetes is more related to lifestyle and genetics. It is caused by fat accumulating around the pancreas, liver and body cells. Insulin is therefore unable to penetrate this fat and get to where it is needed. We call this insulin resistance.

As a result, less glucose enters the cells and thus remains in the blood causing raised glucose levels. Type 2 diabetes is a progressive diseases. This means it tends to worsen over time.

There are a variety of different medications available to treat type 2 diabetes. Each work in their own unique way and should be personalised the each patients own circumstances.

Sometimes patients can be left on medications for too long or not receive a titration in their meds once the disease begins to progress. As a result, you may require an increase in your medication requirements.

2. Too much of a good thing

Like anything in life you can have too much of a good thing. Carbohydrates are the food group which effects your blood glucose levels. If you don’t know much about these I have blogged about them before and you can find that here.

Usually when people think diabetes, they think sugar and so cut out sugar. However, sugar is just one type of carbohydrate and remember, all carbohydrates effect blood glucose levels.

Bread, potatoes, fruit, rice, pasta, cereal, oats, cakes, biscuits, milk sugars etc all effect blood glucose levels. So if you eat too many of any of these your glucose levels will spike.

Some options are better than others such as more slowly releasing carbohydrates like oats, wholegrains, brown varieties of carbs, most fruits, vegetables and beans, pulses and lentils. However, the biggest factor in how your glucose levels respond after eating/drinking carbohydrate is how much you eat or drink.

This means even if it is the healthiest choice imaginable, if you eat too much, you will still see a spike in levels. This is less likely to happen though if choosing lower carb containing foods such as vegetables, beans, pulses and lentils.

The exception

The exception to this is if you inject rapid acting insulin with meals. If you match your insulin to your carbohydrate intake you will not see a spike. However, we still endorse healthy portion sizes because too much food can lead to weight gain.

3. Disease progression

Regrettably if your glucose levels are high for a prolonged period – usually years – it can cause irreversible damage.

Specifically it can cause damage to the eyes, kidneys, nerves, pancreas, heart, blood vessels, limbs, gastrointestinal tract, liver and the list goes on.

Here are some common problems I encounter.


In type 2 diabetes, when glucose levels are high the body senses a problem. The problem is the insulin that is being produced is working inefficiently. The message is not getting through. You are resistant to your own insulin.

The body can’t address this problem directly so it’s solution is to send a signal for more insulin to be released from the pancreas.

If this process is continued over many months and years, the pancreas can actually wear out. Once this happens, managing type 2 diabetes becomes very difficult. At this point you will likely be treated similarly to someone with type 1 diabetes.


Damage to kidneys can also cause problems because they are responsible for excreting insulin. This is primarily a problem for those injecting insulin rather than natural insulin production but this can also be a problem.

If damage has occurred to the kidneys you can begin to see a cycle develop where insulin begins to accumulate in the body. As a result, glucose levels become volatile with large swings between high and low readings.

This can be very difficult to manage.


The liver is responsible for releasing a steady stream of glucose into the body to give it energy. The only time this stops is when insulin tells it to stop. When insulin meets the liver it instead tells it to store glucose as glycogen for later use. Like a squirrel storing its nuts for winter.

If damage occurs to liver, as seen in fatty liver disease (common with type 2 diabetes due to obesity), insulin struggles to tell the liver to stop releasing glucose when it reaches it. As a result, you end up with a constant stream of glucose into the blood. If blood glucose levels are already high, this can increase them even further.

Once the liver reaches the level of fibrosis it is often too late to reverse. Fibrosis is scarring of the liver tissue. Prior to this stage there is scope to reverse some of the damage.

Gastrointestinal system

Chronic high glucose levels can damage the nerves responsible for digestion. This can result in food moving very slowly through the intestines. We call this gastroparesis.

This can hinder diabetes control, particularly in rapid acting insulin users. This is because rapid acting insulin is designed to match the carbohydrates you are eating. However, for the insulin to work the food needs to be digested at a normal rate.

If there is a delay in digestion it is difficult to calculate when to take your insulin and how much to take.


These are just some of the reasons your glucose levels may be elevated. If you still can’t explain why you are having high levels feel free to get in touch with me via email.

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