Vitamin D deficiency is no joke. Bad sleep, bone disease, and respiratory illness — all real possibilities for the half of the global population who don’t get enough of the “sunshine nutrient.” But you’re smarter than that, aren’t you? You want a body that’s bulletproof, and you’ll maximize your vitamin D levels to get it. Luckily, our handsome team of expert biohackers spent years studying the role of vitamin D in the body, and they’re happy to explain how smart daily supplementation can supercharge your immunity and sleep. Wondering how soon you’ll feel better after taking vitamin D? Scroll down and find out.

How Soon After Taking Vitamin D Can You Expect to Feel Better?

Including vitamin D in your daily supplement stack (or nightly as we recommend) is a no-brainer. The benefits are profound: deeper sleep, and far fewer colds and flus. But when will you start to feel these effects? How long before you’ve got that sweet sunshine flowing through your veins? We’ve got two answers for you.

Easy Answer: Generally within a few weeks, but up to 3 months if you’re obese or have a digestive problem like Crohn’s disease.

The More Fun Answer: Sometimes it only takes one night, if the rest of your health and your supplement stack are on point.

The truth is, everything depends on your current blood serum levels…and that’s not easy to predict. 36% of otherwise healthy young Americans (and nearly 60% of general medical inpatients) have a vitamin D deficiency. This shouldn’t be a surprise, since low vitamin D correlates directly with low sun exposure, and very few people get enough healthy sunlight these days.

If you fall in this camp of pale, spindly noodlemen, then a daily, man-sized dose of vitamin D (we recommend 4,000 IU) should top you off in 1-2 weeks. That means if you give blood samples, a doctor will measure, swirl, and sniff, and proclaim you “healthy” based on the numbers.

But doctors’ proclamations have little to do with how you feel.

That’s a good thing, because in our experience, if you stack that man-sized dose of vitamin D with an equally man-sized dose of other healthy sleep-promoting nutrients (like magnesium and zinc), you could wake up feeling like a legend tomorrow morning.

What’s a Vitamin D Deficiency Anyway? Is It Serious?

Technically, doctors consider you vitamin D deficient if your blood-serum levels run less than 30 ng/mL. That’s the official medical opinion. Since we’re concerned with optimal health, however, we prefer to compare our numbers to those of the uber-healthy folks who get plenty of natural sunlight: typically around 50-70 ng/mL.

In general though, as long as you’re around 50 ng/mL, you’re probably okay. You can achieve this fairly easily by spending some time outdoors every day (even on cloudy days), and eating plenty of fish and egg yolks.

What happens if you never go outdoors and earn yourself a vitamin D deficiency? Potentially a lot of bad things.

Researchers have drawn a direct link between low vitamin D and what they call a “world epidemic of sleep disorders.” Persistent poor sleep is deadly. It increases your risk of heart disease, sexual dysfunction, obesity, diabetes, depression, and general grumpiness in the morning.

Vitamin D deficiency can also lead to hypocalcemia, or low calcium levels. Long-term, that can cause a whole mess of thyroid problems, and eventually weak muscles, cramps, fatigue, and once again…depression.

In childhood, severe vitamin D deficiencies can lead to rickets — a terrifying bone-softening disease that leaves kids with deformed limbs. In adulthood, your limbs will stay the same shape, but osteocalcemia will put you at a greatly increased risk of bone fractures.

Trust us. Vitamin D deficiency isn’t pretty.

How Do You Know If You Have a Vitamin D Deficiency?

Symptoms of vitamin D deficiency are a little hard to put your finger on. They typically don’t appear unless your lab numbers fall below 20 ng/mL, and even then, they’re nonspecific. That means it might not feel like you have a serious problem.

In fact, outside of those dreaded bone diseases, these symptoms will probably feel like normal health issues that could have any number of causes:

• Poor sleep
• Depression
• Hair loss
• Headaches
• Muscle weakness
• Fatigue
• Achy joints

Now, you might think that garbage sleep, achy joints, headaches, and general fatigue are a normal part of the aging process. But this is actually good news! If these symptoms are caused by chronically low vitamin D levels, you can knock them out in just a few weeks (or even a few days) with an easy nighttime supplement regimen.

What Does Vitamin D Deficiency Have to Do With Your Sleep?

Honestly, the scientists don’t yet understand the precise role vitamin D plays in sleep. They only know that they’re deeply intertwined.

Hamster studies have found vitamin-D receptors in brain regions responsible for sleep. (Ever seen a hamster sleep? Us neither, but we bet it’s cute.) Similar receptors have been located in human brains, as well as vitamin-D target neurons. How do they modulate your sleep? The guys in white lab coats aren’t entirely sure…yet. But they do know something is up.

Why?

Because studies of people with garbage sleep — insomniacs, nightshift workers, or the elderly for example — have repeatedly found a consistent pattern of vitamin D deficiency. At the same time, researchers have engineered massive sleep improvements by giving these vampirish insomniacs huge doses of vitamin D.

In 2018, a group of intrepid Irani scientists rounded up 89 folks with sleep trouble, gave them astronomical doses of vitamin D (50,000 IU) twice a month, and the results were profound:

This study shows that the use of vitamin D supplement improves sleep quality, reduces sleep latency, raises sleep duration and improves subjective sleep quality in people of 20-50 year-old with sleep disorder.

So, even though we don’t fully understand the function of vitamin D in the brain, we do know that people with a deficiency…well, they just don’t sleep like they should.

What Does Vitamin D Deficiency Have to Do With Your Immunity?

Vitamin D is 100% critical to your body’s ability to fight disease. If you have a deficiency, go ahead and prepare yourself: you’re going to get sick more often, and the sicknesses you get will be worse.

Many of us obsessed over vitamin D during the COVID pandemic, when researchers like Dr. Rhonda Patrick indicated that the healthy levels of the sunshine nutrient reduced the impact of that pernicious virus:

Vitamin D certainly wasn’t a cure for COVID, but studies did show that having levels well above the standard recommendations significantly lowered risk of infection.

This is no surprise. Research has long indicated that vitamin D deficiency increases your risk for respiratory illness like colds, tuberculosis, and asthma. At the same, sufficient levels are essential for activating your general immune defenses, and enhancing function of immune cells like macrophages.

Just as with you natural sleep processes, your body’s immune system simply can’t function at 100% if you have a vitamin D deficiency.

How Much Vitamin D Do You Need On a Daily Basis?

The National Institutes of Health recommend 600 IU (15 mcg) for everyone above the ripe old age of “1”. If you’re older than 70, you can kick that up to 800 IU (20 mcg).

But remember, these “Recommended Dietary Allowances” generally set the bar low. 600 IU may prevent you from getting rickets, but it’s not likely to optimize your health, nor make you feel especially spry.

The NIH also indicates that 4,000 IU is a safe upper limit for your daily needs. This is the same amount of vitamin D we include in Hibernate Sleep Formula, and for good reason. In addition to resolving many sleep and immunity problems, researchers have shown this amount (and even more) can drastically improve other physical qualities.

In 2013, British researchers gave a group of athletes 5,000 IU per day. Eight weeks later, these athletes showed marked improvements in their sprint performance and vertical leap.

The same year, researchers in Utah gave a group of athletes 4,000 IU for 5 weeks. Then, they made them do an absolutely brutal workout: 10 sets of 10 weighted single-leg squat jumps. The results? Those who took vitamin D recovered much more quickly, and saw drastically lower biomarkers representing muscle damage. (Though the vitamin D didn’t prevent muscle soreness, the researchers giddily noted.)

What’s the lesson?

600 IU of vitamin D daily will prevent you from getting bone diseases.

4,000 IU of vitamin D will help you sleep like a baby, fight disease, and make you more athletic.

We’ll take the latter!

How Can You Increase Your Vitamin D Levels Quickly?

There are three ways to increase your vitamin D, though not all of them work quickly.

1. The Slow Option: Food

Eggs, liver, and cheese are all solid choices in the vitamin D department. But, if you really want to increase your levels, one food group reigns supreme: fish.

A single serving of salmon, trout, or cod liver oil will give you at least 20% of your recommended dietary allowance — about 120 IU. Of course, you’d have to eat a TON of fish if you want to reap the maximum benefits of a 4,000 IU dose, and that’s why we don’t think food is a terribly important consideration when it comes to maintaining your vitamin D levels.

2. The Natural Option: Sunlight

The best way to maintain your nutrient levels is always through natural sources. But getting enough sunlight can also be tricky.

The UK National Health Service claims it’s “not known exactly how much time is needed in the sun to make enough vitamin D to meet the body's requirements.”

The trouble is, vitamin D production depends on your skin color and the strength of the sun during various seasons. People with dark skin, such as those of African or South Asian descent, need significantly more time in the sun than our pale friends from Ireland and Norway. If you’re white, living in the Caribbean in June, and running around stark naked, you could manufacture your RDA in 5 minutes. If you’re darker skinned, it could take 30.

The only major concern is avoiding sunburn. (Remember, it’s not sunlight that causes skin cancers, but sunburns). But don’t count the time when you’re wearing sunscreen. The ultraviolet B (UVB) rays blocked by sunscreen are necessary for generating natural vitamin D.

How about time sitting next to your sunny office window? Nope. Glass blocks UVB rays extremely well.

“These many factors explain why vitamin D deficiencies are shockingly common in the United States,” says the Harvard Men’s Health Watch.

Thus, the balance is somewhere in between having a healthy tan, and avoiding burned skin. But what do you do in the middle of a cloudy winter? And what about those who work in an office all day?

3. The Quick, Easy, Healthy Option: Supplements

Luckily, the body doesn’t seem to discriminate between vitamin D synthesized from the sun and that from dietary or oral supplements. “The body can use each perfectly fine,” says Yale Medicine endocrinologist Karl Insogna.

This explains why those noble researchers achieved such amazing effects from dosing athletes and insomniacs with high doses of synthetic vitamin D!

Vitamin D supplements come in both pill and liquid form, and they’re an invaluable resource for people with darker skin-tones (who don’t want to sit in the sun for 4 hours), or folks who live in Alaska (and haven’t seen sunlight since Obama was in office). Capsules are cheap and easily accessible.

Our only recommendation?

You might as well take them in a carefully dosed supplement stack, just so you don’t have to choke down another handful of pills every day.

If You Take Too Much Vitamin D…Is It Toxic?

Indeed, as with everything that’s good for us, too much vitamin D can be harmful. Because it increases calcium absorption, too much vitamin D can lead to hypercalcemia, and in turn, nausea, vomiting, kidney stones, excessive peeing, and bone pain.

Luckily, vitamin D toxicity is extremely rare because it requires astronomical amounts. Multiple studies (1, 2) have shown it’s safe to take doses up to 50,000 or 60,000 IU for extended periods of time, even up to 3 years. That’s 15 times more than we recommend!

Yet, because we all have different levels of sun exposure, calcium intake, and hormonal function, it’s important to remember that excessive vitamin D can cause problems for some people. Anyone with underlying bone, kidney, or calcium-absorption issues should talk to their doctor before they start taking gigantic, unearthly doses of vitamin D.

Conclusion: How Soon Will I Feel Better After Taking Vitamin D?

Vitamin D deficiency is a serious problem, but luckily it’s not a hard one to solve. If you feel like your sleep or immunity have been compromised, good clean eating, daily sunlight, and a solo vitamin D supplement should get you back to normal within 2-3 weeks (or longer if you have underlying health issues).

If you’re like us, however, and want to feel like an absolute champion as soon as possible, there are better ways.

By including vitamin D in a nightly, sleep-enhancing supplement stack, you can start feeling better in only 1-2 days. Why? Because like everything in our bodies, vitamin D doesn’t work alone. It’s just one ingredient in a magnificent symphony of biological processes. When they’re all working together in harmony, everything gets better: your sleep, your immunity, everything.

That’s why we include 4,000 IU of vitamin D in every dose of Hibernate Sleep Formula. We like sleeping hard. We like having bulletproof immunity. We like waking up energetic and ready to conquer each day, and we want you to feel the same way too.