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Can Low Vitamin D Cause High Blood Sugar?

10/06/2022 | 6 min. read

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You know your weight, and you probably know your blood pressure, blood sugar, and cholesterol. But what about your vitamin D blood level? If you’re like most people, you have no idea.

This is worrisome because as many as 90% of Americans are deficient in this essential vitamin—increasing the risk of many common health challenges, from respiratory infections and heart disease to cancer and dementia. Plus, almost every immune system cell in the body has a vitamin D receptor, which is why getting enough vitamin D is so important for the immune system.

Low vitamin D levels are also linked with one of our most rapidly growing health threats, type 2 diabetes.

Vitamin D Deficiency & Diabetes

Every cell in your body requires vitamin D for optimal function, and even subtle deficiencies can cause serious problems. This is definitely the case with type 2 diabetes. It’s easy to see why when you consider vitamin D’s role in blood sugar (glucose) metabolism:

  • Insulin secretion: Your body needs vitamin D to support insulin. That’s the hormone produced in your pancreas that enables glucose in your bloodstream to enter your cells, where it is used to make ATP—your body’s energy. Plus, vitamin D helps to protect insulin-producing cells, called beta cells, which often begin to dysfunction in people with type 2 diabetes.
  • Insulin sensitivity: Optimal levels of vitamin D are required for the normal functioning of insulin receptors—which are the sites on your cells where insulin binds to deliver glucose. Vitamin D also increases the number of insulin receptors, which further improves insulin sensitivity.

Keeping insulin working as it should is extremely important. When your cells become insulin resistant, the pancreas responds by producing more and more insulin to clear glucose out of the blood. Over time, the pancreas just can’t produce enough, and blood sugar is chronically elevated. This is the crux of type 2 diabetes.

Of course, there are many other contributors to diabetes, including obesity, unhealthy lifestyle, age, and genetics. But vitamin D deficiency can be easily corrected.

Robust Vitamin D Levels for Prevention & Treatment

Vitamin D supplementation has enormous potential as an intervention for reducing the weighty burden of diabetes in our country. Maintaining a healthy vitamin D blood level supports normal blood sugar metabolism and protects against type 2 diabetes.

Even if you have a heightened risk, such as prediabetes—blood sugar that is above normal but not quite in the diabetic range—supplemental vitamin D has been shown to reduce the likelihood of progressing to full-blown diabetes if your levels are not sufficient or optimal.

But what if you already have diabetes? Does vitamin D lower blood sugar? To be clear, supplemental vitamin D does not directly lower blood sugar like drugs or natural therapies such as berberine, but it does improve underlying dysfunction that leads to high blood sugar.

Canadian researchers reported that patients with newly diagnosed diabetes who took 5,000 IU of vitamin D daily for six months had improvements in insulin resistance and beta cell function—meaning that the cells that make insulin functioned better.

Why Your Weight Can Affect Vitamin D

There’s one more link between diabetes and vitamin D you should know about. Vitamin D is fat-soluble, so it is stored in adipose (fat) tissue. The more body fat, the more vitamin D is tucked away in storage and the lower your level of circulating vitamin D.

Blood levels of vitamin D are routinely lower in individuals who are obese, and nine in 10 people with type 2 diabetes are obese or overweight.

While researchers are still teasing out the complex relationships between excess weight, insulin resistance, diabetes, and vitamin D deficiency, it all points to the necessity of optimizing vitamin D status.

How to Raise Your Vitamin D Level

There are three ways to boost your vitamin D blood level:

  • Sun exposure: UVB radiation in sunlight initiates a reaction in the skin that triggers the formation of vitamin D3, which is converted in the liver and kidneys into the biologically active form your body can use. To adequately increase your vitamin D stores, several times a week you need to expose bare skin (no sunscreen; SPF 30 blocks 97% of UVB) to direct sunlight during the middle of the day for about 20 minutes—less for people with light skin that burns easily and more for those who have darker skin.
    Note that during the winter, the angle of the sun is such that much less UVB radiation reaches the earth, so vitamin D synthesis drops significantly. Blood levels tend to be lowest in mid-winter, which, not coincidentally, is also peak cold and flu season—since your immune system also needs vitamin D.

  • Diet: Fatty fish like sardines, and especially fish liver oil, are the richest natural sources of vitamin D. Milk, including dairy and most non-dairy plant-based milks, are fortified with vitamin D. (Yogurt, cheese, and other dairy products are not.) Regardless, it’s practically impossible to get all the vitamin D you need from food alone.
  • Supplements: The most practical and reliable way to raise your vitamin D level is with supplements. Vitamin D comes in two forms, D2 and D3. I generally recommend D3 (cholecalciferol) because it raises blood levels more effectively. I also recommend taking a product that contains vitamin D3 along with cofactors that enhance absorption and bioactivity. These include vitamin K2 80 mcg, magnesium 100 mg, zinc 5 mg, and boron 3 mg.

How Much Should You Take?

I am often asked how much vitamin D you should take. It’s a great question, and I wish I had a pat answer, but there is no single dosage that’s best for everybody. If you don’t know your vitamin D blood level, a good starting dosage for most people is 5,000 IU (125 mcg) of vitamin D3 per day.

But I do encourage you to test your blood level. The main form of vitamin D circulating in your body is 25-hydroxyvitamin D or 25(OH)D, and it is what is measured on blood tests to determine vitamin D status. The goal is to maintain your 25(OH)D level in the therapeutic range shown in clinical trials to produce the best health outcomes: 40-60 ng/ml. That’s the sweet spot!

You can ask your doctor to order a 25(OH)D blood test, although some physicians are reluctant unless you have a condition suggestive of a glaring deficiency. Fortunately, vitamin D testing doesn’t require a prescription, and several organizations offer at-home test kits. The kits I recommend are from Grassroots Health, a wonderful nonprofit foundation that promotes vitamin D awareness. Their kits are easy to use and test results include the recommended dosage to keep your level in the ideal range.

The Bottom Line: Be Proactive & Take Vitamin D

I believe that monitoring and staying on top of your vitamin D level is as important as controlling your blood sugar and weight. It’s particularly important for certain groups. An astounding 97% of African Americans are deficient in vitamin D. That’s because darker skin is less efficient in producing it, which is something that often affects Latinos as well. Plus, older adults and people who are obese, get limited sun exposure, or have a history of gastric bypass surgery or a condition that limits fat absorption are also more likely to be deficient.

Maintaining an optimal level of vitamin D is a proven preventive strategy, not only against diabetes and prediabetes but many other common health problems. That’s why I am on a mission to increase awareness of vitamin D levels and the importance of taking supplements to correct deficiencies.

This simple, affordable, and accessible step can make a tremendous difference in the health of our country. Help me get the word out!

Dr. Ken Redcross

Meet Dr. Ken Redcross

Board-certified internist and best-selling author, Dr. Ken Redcross helps patients achieve remarkable health outcomes by addressing overlooked metabolic imbalances and nutrient deficiencies.

More About Dr. Ken Redcross