How to Fix Low Vitamin D Levels

How Vitamin D Deficiency Is Treated

Vitamin D deficiency is relatively easy to fix and most people will achieve normal levels within two to three months if the proper protocol is used. The main issue is ensuring that the dose of vitamin D taken is appropriate for your degree of deficiency.

Supplementation Is the Primary Fix

While diet and sunlight do help improve overall vitamin D status, they rarely completely correct a true deficiency on their own. Vitamin D levels in food are extremely low typically and sunlight-driven production is very dependent upon location, time of year, and extent of skin exposed. For many people, relying solely on diet and sunlight would likely be impractical and ineffective.

Supplementation is generally considered the most convenient and best-supported method for addressing a true vitamin D deficiency. When selecting a supplement, vitamin D3 (cholecalciferol) is generally recommended over vitamin D2 (ergocalciferol). Research has demonstrated that vitamin D3 is significantly superior at raising serum 25-hydroxyvitamin D levels versus vitamin D2. [Source: Tripkovic et al., 2012] Vitamin D3 is also the natural form produced in the skin from sunlight, which is part of why the body utilizes it more efficiently.

Dosing Depends on How Low Your Levels Are

Not everyone with low vitamin D needs the same dose. The Endocrine Society’s clinical practice guideline provides a tiered treatment framework based on severity:

Insufficient (20-29 ng/mL): 1,000-2,000 IU of vitamin D3 daily is typically enough to bring levels into the sufficient range within 2-3 months. This is the mildest form of “low vitamin D” and often responds well to over-the-counter supplements.

Deficient (below 20 ng/mL): The guideline recommends 50,000 IU of vitamin D2 or D3 once per week for 8 weeks, followed by a daily maintenance dose of 1,500-2,000 IU. This higher-dose loading phase is needed because standard daily doses take too long to correct a true deficiency.

Severely deficient (below 12 ng/mL): The same 50,000 IU weekly protocol applies, but treatment may need to extend beyond 8 weeks depending on how your levels respond. This should be managed by a physician with follow-up blood work to confirm progress.

Once any corrections are made, the goal is to establish and keep 25(OH)D concentrations above 30 ng/mL (75 nmol/L).

How to Get the Most from Your Vitamin D Supplement

Determining the appropriate dose is half the battle but the way you take your supplement, also affects how much your body actually absorbs.

Take It with a Meal Containing Fat

Vitamin D is a fat-soluble vitamin. It requires dietary fats to be appropriately absorbed in the gut, so taking vitamin D with a meal that contains little to no fat, or on an empty stomach, decreases absorption. Studies have shown that ensuring the meal does have enough fat, increases absorption by approximately 50% compared to taking it on an empty stomach or with a fat-free meal.

The practical takeaway: take your vitamin D supplement with whichever meal contains the most fat, and for most people, that’s lunch or dinner. The amounts of fat do not need to be large. Olive oil, fatty meat or fish, cheese or a small handful of nuts alongside your dose is enough.

Daily Dosing vs Weekly Dosing

Another question that comes up frequently is whether daily or weekly dosing produces better results. The answer: it really does not matter much, as long as you are achieving the equivalent total dose. Taking 1,000 IU daily provides a total of 7,000 IU per week. Taking 7,000 IU weekly provides the same total. Both methods produce comparable improvement in blood levels over time.

The 2024 Endocrine Society guideline supports using daily lower-dose supplementation as opposed to intermittent higher doses for long-term prevention. But in terms of practicality, whichever schedule you’ll actually stick with consistently is the best option.

Why Obese Individuals Need Higher Doses

Standard doses of vitamin D may not be enough if your BMI is above 30. Because vitamin D is fat-soluble, it gets trapped in adipose (fat) tissue instead of circulating freely in the bloodstream. As a result, a larger portion of each dose accumulates in the tissues rather than being used.

The Endocrine Society guideline notes that obese individuals may require two to three times more than standard doses to achieve similar blood levels as someone at a normal weight. If the recommended maintenance dose is 1,500-2,000 IU daily, someone with a BMI over 30 might need 3,000-6,000 IU daily. As always, the result a particular dose has on you specifically should be confirmed through blood work.

Can You Fix Low Vitamin D with Food and Sunlight Alone?

Unfortunately, generally not. Both contribute to maintaining adequate levels after correcting a deficiency, but neither is usually capable of reliably correcting one independently.

Food Sources of Vitamin D

The richest natural sources include fatty fish (salmon, mackerel, sardines), cod liver oil, egg yolks, and fortified foods like milk and some cereals. But the amounts are relatively small compared to what deficiency correction requires. One serving of salmon provides approximately 400-600 IU. To achieve 2,000 IU daily just for maintenance, you would have to consume salmon at nearly every meal.

We break down the full list in our guide to foods high in vitamin D. Use food as a supplement to your supplement, not a replacement for it.

Sunlight Exposure

Your skin produces vitamin D when exposed to UVB radiation from sunlight. Although theoretically you could get adequate vitamin D from 10-30 minutes of direct midday sun on your arms and legs several times per week, there are many factors that are difficult to control:

• Latitude: above 35 degrees north, UVB exposure is insufficient during winter months
• Skin pigmentation: darker skin requires longer exposure to produce the same amount
• Season: UVB radiation is weaker in winter
• Cloud cover
• Sunscreen use: SPF 30 blocks roughly 97% of UVB radiation

If your location is appropriate, you could try raising your levels with sunlight, but it requires disciplined daily exposure, enough to trigger vitamin D synthesis but not so much that you get sunburned.

Time of day matters too, and even if location and schedule align for this approach to work, you’re still increasing your risk for skin cancer. Still, even if that is ignored, for your levels to last you through the winter, you need to sunbathe so much in the summer that they reach very high values.

If you live in Greece or southern Europe, sunlight can provide significant contributions from late spring until early fall. But those living in northern Europe, Canada, or the northern US cannot rely on sunlight for roughly 4-6 months of the year.

Sunlight helps maintain levels. It is not a reliable vitamin D deficiency cure on its own.

How Long Does It Take to Fix Low Vitamin D?

Most people want to know when they’ll start feeling better. Here is a realistic timeline:

Relief from symptoms (fatigue, mood): approximately 4-8 weeks of consistent supplementation at the proper dose. This is when most people feel their fog lift and experience increased energy.

Blood level correction: 2-3 months to move from deficient to sufficient range. The length of time depends on your starting level, your dose, your body weight, and how consistently you take your supplement.

Maintenance After Your Levels Are Corrected

Correcting a deficiency is a one-time process, but maintaining healthy levels is another matter. If the causes of your deficiency remain while you stop supplementing, your levels will decline once again. If you spend most of your days indoors, live above 35 degrees north latitude, have darker skin pigmentation, are obese, or have a malabsorption condition, maintenance supplementation of 1,000-2,000 IU daily may be necessary indefinitely.

For most adults without specific risk factors, 600-1,000 IU daily is typically enough to maintain healthy levels. High-risk individuals should have their levels tested annually or biannually to ensure they remain adequate. Also, don’t assume that more is always better. There is an upper limit to the amount of vitamin D you can safely take. Chronic intake above 10,000 IU daily can lead to toxicity, causing dangerously elevated calcium levels. We cover the details in our guide on vitamin D toxicity.

For a broader look at everything vitamin D does in your body, see our vitamin D benefits article. If you’re not sure whether your symptoms point to low vitamin D, our breakdown of vitamin D deficiency symptoms can help. And if you’re ready to choose a supplement, our guide to the best vitamin D supplements reviews the top options.