High waking glucose levels & how to fix them T1DM

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Fixing high waking glucose levels introduction

Having high waking glucose levels in type 1 diabetes can throw the rest of the day out. As if it isn’t already enough that you need to think about work, family, household chores etc, you then also need to combat your diabetes.

Therefore, its no surprise one of my most common questions I get from my patients with type 1 diabetes is why do they have high waking glucose levels. The principles I am going to discuss work whether you’re on pump or subcutaneous injections. The management may be slightly different as the pump offers more flexibility but the principles remain the same.

Here I’d like to share 4 of the reasons why this happens and explain what you can do to fix them.

Not enough background/basal insulin

The first reason you may have high waking glucose levels is because you do not have enough background insulin. Your background insulin prevents your liver releasing too much glucose into the blood. Overnight (assuming you’re asleep), the only variable effecting your glucose levels is the liver. There shouldn’t be any rapid insulin in your system unless you eat just before bed. Exercise may have an effect if you exercised earlier in the day but what I’m about to explain I’d suggest having a day off exercise.

This then only leaves how much glucose your liver releases. If you go to bed in target glucose range and wake up high, it’s an indication your background insulin is insufficient.

What to do about this

However, it’s always worth double checking this whilst awake. You can do this by having some carb free meals and not exercising to see what happens to your glucose levels in the day. This is called a basal test. If they begin to significantly rise despite no carbohydrate in your meal, it’s likely the background insulin is off. Conversely, if they begin to drop, it likely means you have too much background insulin.

If this is the case, adjust your background insulin in 10-20% steps and repeat the process.

An overnight hypo

You probably don’t need me to tell you that a hypo can really mess up your glucose control. High waking glucose levels can also be caused by hypos. This is because even without treating a hypo your brain recognises the hypo and tells your liver to release glucose to help treat it. You can therefore get a rebound effect even without treating the hypo. This doesn’t mean you shouldn’t treat the hypo but the liver does help.

The first thing is to figure out is what causes the overnight hypo. If the hypo occurs within 4-6 hours of your last meal, it’s likely related to your rapid insulin dose. Especially if your glucose levels dropped quit abruptly e.g. from 10mmol/l down to 3mmol/l.

If the drop is more gradual it is likely caused by your background insulin. Only this time, it means you have too much background insulin. This is why in point 1 I always recommend testing your background insulin with some carb free meals. Had you had high waking glucose levels and presumed your background insulin is insufficient and increased it, you’d have actually worsened your hypo. This could be very dangerous.

What to do about this

Though it is rather counterintuitive, in this case you need to reduce your background insulin to prevent the high waking glucose level. If you’d prefer not to do that you can always have a bed time snack to counteract the drop in your glucose levels but then you are feeding your insulin. From experience this can solve the hypo problem but cause weight gain, especially if you are also having to treat hypos throughout the day.

3. The Dawn Phenomenon

Now in point 1 I told a slight lie. I said only the liver effects your glucose levels overnight. There is one more factor at hand here. Hormones can effect your glucose levels, particularly overnight.

As you prepare to wake up in the morning your body releases hormones to prepare you for the day. The problem with this in type 1 diabetes is it can increase your waking glucose levels.

This will usually occur in the early hours of the morning. Despite your background insulin being at the correct dose, you’ll suddenly see a dramatic rise over a couple of hours.

The use of continuous glucose monitors has allowed us to see this in greater detail. If you do not use these, a good way to test this is to see what your glucose levels are around 10pm, 12am, 2am and then upon waking. It’s a pain to wake up so often but it could be worth it in the long run if you can sort the problem.

What to do about this

If you do find your high waking glucose levels are caused by the dawn phenomenon, there’s a couple of actions you can take. If you are using injection pens, unfortunately, you will just have to correct this high reading upon waking or overnight. If you aren’t familiar with corrections I’ve discussed them here before. If you are on pump therapy you can adjust your basal insulin for that specific time slot to help counteract the hormones. So the pump is much more flexible. Again, I’d recommend only adjusting small amounts at a time so not to over do it. 10-20% works well.

Post dinner glucose level

I save arguably the most common for last. One of the reasons for your high waking glucose levels is because you went to bed with high glucose levels.

Your background insulin ideally should not cause big swings in your levels. For example, if you consistently go to bed with a glucose reading of 15mmol/l and wake up with a levels between 5-7mmol/l, you might be happy. This is because you have woken up in target. However, your glucose levels have dropped 8-10mmol/l overnight. Had you gone to bed with a glucose level of 9mmol/l what would your waking glucose level have been then? You’d have likely suffered a huge hypo.

Ideally the background insulin holds your glucose levels reasonably steady overnight, even if they are high. This is why the basal test in point 1 is important. Once we know the basal insulin is correct, you can then start to play around with your rapid insulin. In this instance, we now know it must be rapid insulin causing the problem because you have tested the background insulin with a basal test.

Therefore, if you go to bed with a glucose level of 15mmol/l and wake up somewhere around that, having done a basal test, the problem is going to bed high not insufficient background insulin. If you go to bed at 15mmol/l and wake up at 15mmol/l that’s ok because we can fix this. If you go to bed with a glucose level of 8mmol/l you’ll likely wake up with a glucose level of around 8mmol/l.

What to do about this

If this is happening to you, look at the pre meal glucose level and compare it to the bed time glucose level. If the glucose levels rise, it means you aren’t giving enough insulin at dinner.

If the pre and post meal glucose levels are similar but remain high, it means you need to give more correction insulin.

If the glucose levels continue to rise over 4 hours after the meal it might mean the meal is being slowly absorbed and you might need to split your injection to before and after the meal. If you’re on a pump deliver a different type of bolus e.g. square wave.


There you have it all. Four reasons that may cause high waking glucose levels. I hope you have found it useful. This is only general advice and you will need to apply it to your individual circumstances. Remember, when it comes to insulin, if you aren’t sure, ask your GP, DSN or diabetes team.

Need more help

If you need more support we offer a range of 1:1 consultancy services and online programmes focused on helping you improve your glucose control and health for the long term. These include our type 2 diabetes recovery programme, type 1 glucose stability programme and winning weight loss programme. Go to the pages using the links above or in the headers or get in touch if you have questions.

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