Can Hypothyroidism Cause High Blood Sugar?

The answer is yes!

But what I find in most patients is that the primary cause of high blood sugar is typically not the thyroid (although it certainly can contribute). 

Instead, there are several other conditions such as the amount of stress that you are under, what type and how much thyroid medication you are taking, the foods that you are eating, and more. 

In this article, we are going to discuss the nuances of managing high blood sugar if you have hypothyroidism and include some takeaway therapies as well

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High Blood Sugar Stems from Insulin Resistance (& Sugar Consumption)

Treating high blood sugar is incredibly important from an overall health perspective but also from a weight loss perspective. 

Why?

Because the fact that you have high blood sugar is usually a sign of something known as insulin resistance

You've probably heard of insulin in the past but perhaps you didn't really understand its significance. 

It's important to understand these basics so you can understand how your thyroid impacts both insulin and blood sugar. 

So what exactly is insulin?

Insulin is a hormone secreted by your pancreas typically in response to food (1) (but stress can also stimulate it). 

relationship between insulin resistance, blood sugar, and hypothyroidism

Your body produces insulin after you eat a carbohydrate-rich meal because it wants to utilize the energy you just consumed. 

Insulin directs your blood sugar INTO your cells. 

And this is a good thing (typically). 

But there is a difference between insulin the hormone and insulin resistance. 

Insulin resistance is a state of cellular resistance to insulin which occurs in response to repetitive and repeated carbohydrate (sugar) intake. 

And that's when things start to become a problem. 

As your body becomes resistant to insulin, your blood sugar will rise because your body has a harder time putting inside of your cells. 

This leaves it floating around in your bloodstream instead of inside of your cells where you want it. 

So how does your thyroid fit in?

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Hypothyroidism and Blood Sugar

It turns out that your thyroid is actually a potent modulator of both insulin and glucose (sugar) metabolism (2). 

What does that mean?

It means that if there is something wrong with your thyroid function then it will almost always affect your blood sugar in some way. 

And, by the way, this is separate from other issues which can ALSO cause insulin resistance. 

It's certainly possible that you have high blood sugar from a diet rich in carbohydrates (sugar) which is ALSO made worse by the fact that you have hypothyroidism. 

Thyroid hormone, under normal conditions, is supposed to act to help your body get rid of excess sugar inside of your cells. 

In this way, it opposes the action of insulin. 

The interplay of thyroid hormone and insulin/blood sugar is actually more complex than that (3), but this serves to drive home the point. 

If there is an issue in thyroid status (meaning that your thyroid levels are abnormal) then it will always affect your blood sugar and insulin receptor sensitivity in some way. 

It's best to think of the connection between thyroid function and blood sugar as a balance. 

If thyroid hormone is too low then it will result in high blood sugar and insulin resistance. 

On the flip side, if thyroid hormone is too high then it will also result in insulin resistance and high blood sugar. 

You want your thyroid status to be just right in order to balance blood sugar. 

This also means that patients with hypothyroidism (which is incredibly common, by the way) are at a distinct disadvantage when compared to other healthy people. 

Why?

Because the current treatment paradigm for hypothyroidism may leave up to 20% of thyroid patients 'undertreated'. 

Does Thyroid Medication Worsen or Treat Insulin Resistance?

One question that I am asked frequently has to do with thyroid medication and whether or not it helps or hurts blood sugar. 

The answer is that thyroid medication only impacts blood sugar insofar as it impacts thyroid function in your body. 

What do I mean?

It means that it depends on how much you are taking and how much your body actually needs. 

It's possible for thyroid medication to make insulin resistance (and blood sugar) worse but it's also possible for thyroid medication to improve your blood sugar. 

It depends on how much you are using. 

Remember:

Thyroid medication is always taken to treat a deficiency of thyroid hormone in your body. 

But taking thyroid medication is NOT the same as allowing your body to produce thyroid hormone on its own and we are never quite as good as your own body is at that. 

If you take too much thyroid medication (T4 or T3) and you become hyperthyroid based on certain lab tests, then you may raise your blood sugar,

I don't find this to be common for most people because most people are not taking enough thyroid medication. 

The situation I see in most patients is that they are not taking ENOUGH thyroid medication or the right type of thyroid medication. 

This generally leads to persistently high blood sugar (and insulin resistance (4)) and the inability to lose weight. 

If you take the right type of thyroid medication (usually a medication which contains a combination of both T4 and T3) it's usually much easier to lose weight and it has to do with thyroid status in your body (not the medication itself). 

Cortisol, Blood Sugar & Thyroid Function

The connection between your thyroid and blood sugar goes even deeper than what I've already explained so far. 

There is a further connection between your thyroid function and your stress levels that we also need to address. 

A quick recap first, though:

We know that hypothyroidism (or hyperthyroidism) can lead to high blood sugar. 

This blood sugar issue can be treated with the use of thyroid medication. 

But what about stress and cortisol?

There is another deeper connection between cortisol and your TSH (another way to describe the fact that cortisol impacts thyroid function). 

Physiologic studies have shown that as cortisol rises it also tends to bring up your TSH (5). 

the rise in cortisol triggers a rise in TSH

For those unaccustomed to understanding the nuances of TSH, a rising TSH is an indication of HYPO (slowing) thyroid function. 

So, what does that mean for you?

It means that stress can cause a decline in thyroid function by itself. 

So now we have a system that looks like this:

Stress = decreases thyroid function = increases insulin resistance = increases blood sugar = increases your weight

And it doesn't stop there. 

We also know that stress by itself can stimulate the release of blood sugar and insulin resistance on its own (6)!

In this way, it's probably more important for you to manage stress (if you are suffering from it) than it is to focus on your thyroid to directly impact both your thyroid and your blood sugar. 

A high amount of untreated and repeated stress can lead to weight gain from insulin resistance which usually manifests as an increase in belly fat (not ideal for most people!). 

The bottom line?

If you have high blood sugar and hypothyroidism, you should also make sure to consider testing your cortisol and managing your stress. 

By addressing both your stress and cortisol you may be able to indirectly impact your thyroid function. 

The Impact of your Diet on Blood Sugar

Another area which is worth going into some more detail is that of your diet and its impact on your blood sugar. 

I touched on this in the very beginning but not for long. 

When most people think about high blood sugar they often think immediately of the food that they put in their mouth (7). 

It just makes logical sense that if you eat a meal high in sugar that it will then increase your blood levels of sugar and this is largely true. 

Imagine consuming a 44-ounce big gulp (or whatever they are called near you) of Coke or Pepsi loaded with high fructose corn syrup. 

All of that sugar is going to be rapidly absorbed into your body and trigger the release of insulin as we've discussed previously. 

But other foods are also high in blood sugar and more than just carbohydrates can stimulate the same response. 

Starchy foods, potatoes, fruits, etc. can all be absorbed and stimulate the insulin response as well. 

The main difference between these foods and the big gulp example is the rate of absorption and how this rate impacts the rise of insulin levels from the pancreas (8). 

Because of this, healthy whole foods are nowhere near as hard on insulin levels as foods with rapidly absorbed sugar. 

In addition to this, high sugar foods which are consumed with high fat also exacerbate and contribute to insulin resistance. 

I've found that it's generally safe for most people (not all) to consume whole foods which are high in 'sugar' if they don't consume them with high fat (even healthy fats (9)). 

Beyond this relationship, it's also important to note that even foods high in protein can also stimulate the insulin response. 

The only macromolecule which has the smallest impact on insulin by itself is fat. 

Because of this, many doctors and providers have started recommending diets which are very high in fat as a treatment for high blood sugar and insulin resistance. 

But there is a problem with this approach... it doesn't always work!

*Note though, that it does at least a majority of patients but it's often insufficient to completely reverse insulin resistance by itself. 

There are plenty of people who go on ketogenic diets and high fat & low carbohydrate diets but yet they still experience high blood sugar and weight gain. 

This just highlights the fact that we need to better understand the relationship between blood sugar and insulin. 

My opinion is that there are other factors outside of just your diet that contribute such as subclinical thyroid dysfunction and cortisol dysregulation (as we've discussed above). 

Treating Insulin Resistance if you have Hypothyroidism

So, what are you supposed to do if you have high blood sugar and hypothyroidism and you want to treat it?

What if you want to treat insulin resistance to help you lose weight?

There are several strategies that you can take and I've listed several below:

  • Optimize your thyroid medication - What I mean here is that you need to make sure that your thyroid medication is optimized for your body. For most of you, that means you will probably need to take more than you are currently taking. For some that may mean lowering your dose. When optimizing your medication for blood sugar, you'll want to focus less on the TSH and more on your free thyroid hormones (free T3 and free t4). As you optimize both of these numbers you will probably find that your blood sugar will drop naturally. Avoid increasing these numbers outside of the reference range while trying to optimize them in the top percentile of the "normal" range. You can learn more about this concept here.
  • Take insulin sensitizing supplements - There are several supplements (which are available over the counter) which you can take in conjunction with all of the therapies I've listed here, which can help improve your blood sugar. Some of my favorites include Berberine, fish oil, Alpha lipoic acid, and chromium. These supplements all have scientific studies which show that they are effective at reducing both blood sugar and insulin resistance. And the best part is that they can be taken or used in conjunction with medications and other lifestyle modifications.
  • Take insulin-sensitizing medications - If you really want to kick things up a notch you can also try the use of insulin-sensitizing medications. These medications are particularly useful if you are struggling with weight loss resistance which you believe is secondary to insulin resistance/high blood sugar. These medications can be used temporarily (to reverse the condition) and don't necessarily have to be taken long-term for you to realize their benefits. Medications which fit into this category include Victoza, Saxenda, and Metformin. There are others, but these should serve as a good basic framework for you to look at. Victoza and Saxenda are quite expensive if insurance doesn't cover them while metformin is incredibly cheap at around $4.00 per month. The downside to using Metformin is that it's not quite as effective as the others, but it's a great medication to use in many people. Metformin (and the others) can also be used in conjunction with supplements with may enhance their potency and effects!
  • Exercise correctly - We didn't talk much about exercise in this post, but it's certainly an important aspect if you are trying to lower your blood sugar. Exercises which put a temporary high strain on the body over a short period of time tend to be best at improving insulin sensitivity. Exercises that fit into the high-intensity interval training spectrum are often ideal. The good news is that you don't need to spend hours on a treadmill but the bad news is you will need to push yourself to get results.
  • Clean up your diet - Another thing you'll want to do no matter which therapies you use is adjusting your diet. Taking all the supplements, medications, and thyroid hormone in the world will not be enough to counteract the negative effects of a bad diet. Most people know what 'healthy' foods are, but even if you aren't sure then look to a diet such as Whole-30 as a guide. Diets which are high in real, whole foods are your best bet.
  • Consider other medications such as LDN - Lastly, some other medications can also be used to help sensitive your body to insulin. Medications like LDN (low dose naltrexone) can also potentially help autoimmune disease states such as Hashimoto's thyroiditis (a major cause of hypothyroidism). These medications are often prescribed off-label though, so you may need a willing physician to help you out.

As you consider these therapies just keep in mind that the more therapies you add on top of each other the more likely you are to see your desired results.

That means you'll want to simultaneously change your diet, take the right supplements, adjust your thyroid medication, exercise sufficiently, and consider other medications to normalize your weight and blood sugar.

Conclusion

While it is true that hypothyroidism can lead to high blood sugar, the connection between the two is not just that simple. 

There is a range of competing factors which can also contribute to high blood sugar in hypothyroid patients which should also be evaluated. 

The good news is that you can lower your blood sugar by taking several steps such as adjusting your thyroid medication, taking supplements, and improving your lifestyle. 

Lastly, never forget the connection between stress, your thyroid, and your blood sugar. 

Many people out there right now are probably suffering from a combination of all 3 while not even realizing it. 

If you haven't already, I would encourage you to look at therapies (supplements) which can help your body tolerate more stress than it would be able to otherwise. 

These therapies have the potential to help improve your energy levels and may also improve other hormone systems in your body. 

But now I want to hear from you:

Do you have hypothyroidism? 

Do you also have high blood sugar?

What have you done to try and treat your blood sugar?

Do you feel that stress is contributing to your situation?

Leave your comments or questions below! 

References (Click to Expand)

Dr. Westin Childs

Dr. Westin Childs is a Doctor of Osteopathic Medicine. He provides well-researched actionable information about hormone-related disorders and formulates supplements to treat these disorders.He is trained in Internal Medicine, Functional Medicine, and Integrative Medicine. His focus is on managing thyroid disorders, weight loss resistance, and other sex hormone imbalances.You can read more about his own personal journey here.

12 thoughts on “Can Hypothyroidism Cause High Blood Sugar?”

  1. When is the best time to do Lab draws? Take or do not take my thyroid (Amour) before the blood draw? How much time between blood draw and ingestion of thyroid meds? Thank you.

  2. Hello Dr Childs,

    I have Hashimotos disease (looking at my blood test results I think I have had an underactive thyroid for over 20 years)/ I started to put on weight when I turned 40 and have looked at my blood test results from that time and TSH was 3.8 (range then 0.3-5.0) and T4 was 11 (range then 9.0-24.0). It became Hashimoto’s when my mother and my husband died within 6 months of each other (although as antibodies were never tested, I will never know). It was extremely difficult time, battling the NHS for over 6 months for my mother who was profoundly deaf and also looking after my husband who died within 3 months of being told he had terminal bowel cancer.

    I believed at that time that I have adrenal fatigue, but was dismissed by endos, who had no idea what I had been through and didn’t really want to know. I have been on levothyroxine for almost 7 years since the Hashi’s diagnosis. Over this past year HbA1c has now increased over this past year to 47 (1 point short of being diagnosed as T2 diabetic). My blood pressure has increased too, although my heart rate has always been in the 50s/60s (very occasionally in the 70s) and my basal temps are low too.

    My TSH has always been low on levo and I’m always being told I’m over medicated – I’m most certainly not.TRH test was done with no response and I had an MRI scan of pituitary which they said was normal – they don’t know why TRH didn’t respond.

    Earlier this year after being on 150mcgs of levo and still having extreme fatigue and difficulty losing weight, I was finally prescribed T3 to be added to my levo of 150mcgs (was told to reduce to 100mcgs). I did this and initially saw a slight improvement in fatigue, but in the meantime, I did the genetic test for DIO2 and found out I am heterozygous for DIO2. The endo said I could increase T3 to 30mcgs. I did this and immediately put on nearly 1 stone in weight in a month and started to experience edema (pitting of the skin).

    I came off all meds for 10 days and had a blood test. My TSH raised to 9.7 (proving that there is no problem with my pituitary). I started on levo and gradually raised it back to 100mcgs and then added T3 in first 10mcgs and then raised to 20mcgs. Through following a very low calorie diet, I have managed to lose the extra weight I gained on the T3 increase, although it took me a month to do it. My endo said I could increase levo to 125mcgs and I have kept T3 at 20mcgs. He actually admitted that TSH is irrelevant when on T3 and that I am one of the 20% who still struggle when my bloods are in “normal” range and that I would probably feel better at the top end of range for T4 and T3 (I did manage to lose 3 stone when I was top end of normal), but I was left with no endo support for a year and as my thyroid continued to falter, my meds were not increased and so I gained all the weight back as well as becoming increasingly hypothyroid. At my last appointment in October, the endo suggested that I medicate to how I feel!! I do feel a little better on the newest dose, however, I am scared to raise the T3 as I’m worried about edema and weight gain again (which would of course increase my blood sugar and blood pressure).

    No one seems concerned about my weight, my GP shrugs his shoulders and says it’s your thyroid. He’s admitted he doesn’t know how to treat hormones. I have resisted going on meds for my high blood pressure, but I’ve had a letter from my GP following my last blood test which shows HbA1c of 47 and I think they’re going to suggest medication.

    I also have Thyroid Eye Disease(for almost 3 years) and have proptosis in right eye and lid lag in left eye. They were extremely concerned about my eye pressures but they have reduced a little with special overnight eye drops. The hospital say that TED is now inactive and that I can be scheduled to have an operation on lid lag eye.

    Since my Hashi’s diagnosis in 2012, I have calculated that I have seen 14 endos/nurse practitioners (excluding GPs and eye specialists) and I seem to be collecting other issues along the way.

    The upshot is I am about 4 stones overweight, have unmedicated high blood pressure and unmedicated pre-diabetes.

    I have also been diagnosed with a small posterior fossa meningioma (discovered at the MRI for my TED) for which I amon watch and wait. I have Dupytren’s contracture following a broken wrist. The good news is that the osteopenia diagnosed from a DEXA scan at the end of 2015, has reversed at my last scan in May and I now no longer have osteopenia. My spine is normal and my hips are low, but normal.

    I would add that I am post-menopausal.

    My last bloods were TSH <0.05 (0.5-5.0), FT4 14.2 (10.0-22.0) FT3 5.3 (3.6-6.4).

    I firmly believe that my hormones are severely unbalanced, and this is the reason for my continuing symptoms and issues but no-one seems interested in this and the medics seem unable to help me to balance them.

    Any help you could offer would be much appreciated.

    Thank you.

  3. Great article Doc yes both my wife and I are having huge struggle with weight since our thytoiddectomy hers cancer mine graves. She is also struggling with diabetes for me it’s high weight gain. I’m on nature Throid now 3 months it’s hard to find keep having to juggle the script for what’s available. Liked you idea of splitting the dose and that would help the availability nonsense. I am on 2.5 gr it’s easy to get the lower dose 1.5 gr evening and 1 gr in am. I am going to get your thyroid supplements keep the info coming. It’s hard coping without this amazing gland.

  4. Hello. You mention over-exercising. What are the symtpoms, or how do I know if I’m over exercising? I’m a third-degree black belt in Shaolin kung-fu, and twice a week, I help teach a kid’s kung-fu class, then do tai-chi, then do black belt material. For two days following, I can barely move from muscle cramps and fatigue, and I’m exhausted. Two other days a week, I do yoga/mobility. Am I taxing my body too far? Background: I had a total thyroidectomy in 2009 (papillary cancer), and a recurrence of cancer in my lymph nodes in 2015. Current labs: TSH 3.43; T3 1.193; T4 .44. Thanks so much. Love your site, it’s very informative!

  5. Forgot to mention–I was diagnosed with insulin resistance 25 years ago, and currently have high blood sugars as well. Thanks.

  6. Dr. Childs,

    Thank you so much for the information that you share. I’m still learning and you are a wealth of knowledge on this subject.

    I believe that I have been hypothyroid since birth, but wasn’t diagnosed until age 7, when the doctor said that about half of my thyroid gland did not function. I’m now 60 and currently taking NP thyroid, 4 grains (240 mg). (was on Armour for years before they went outrageously expensive). I’ve always had difficulty losing weight. I also have type 2 diabetes and am having trouble getting my blood sugar down, even when I went totally off of starches and sugars. I even had a bout of depression a few weeks ago, after about a week of eating good quality protein, non-starchy vegetables, and good oils. I was crying at work on and off one day at work, and didn’t know what was causing it. Is it possible that the lack of carbs was causing my thyroid to slow down, which caused the depression? I gave in that evening and ate something with sugar in it, and the depression stopped. It hasn’t come back since then when I started eating one fruit a day. This is a juggling act with me having both of these conditions. A ketogenic diet simply doesn’t work for me. I will stall if I eat too much fat, and get tired and depressed from eating too few carbs. Then I’m told…. don’t go too low on your calories, yet I lose very slow even on a 1200 calorie diet. The only time I’ve lost consistently was on a very low calorie diet, but was balanced. Can you give me any suggestions? Thanks for reading this.

  7. Thank you very much for this article. I have been experiencing very bad morning headaches as I have increased my T3 dose. My fasting blood sugar is 6.6 and I eat basically no sugar and very limited refined carbs. Your article provides a potential explanation and I’m very grateful for this. What I’m not totally sure of is how low cortisol can impact blood sugar? Is the effect the same as high cortisol???

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