vitaminOTC supplementHigh-dose ergocalciferol (e.g., 50,000 IU capsules) is an FDA-approved prescription product for vitamin D deficiency in the USLower-dose ergocalciferol is also sold over the counter as a dietary supplementThe pooled meta-analysis found vitamin D3 raised serum 25-hydroxyvitamin D more effectively than D2
Vitamin D2 (Ergocalciferol)Benefits, Dosage & Interactions
Also known as: D2
Vitamin D2, also known as ergocalciferol, is one of two primary forms of vitamin D, the other being vitamin D3 (cholecalciferol). Both D2 and D3 are prohormones that the body converts into calcitriol, the active form of vitamin D. Research on Vitamin D2 (Ergocalciferol) focuses on heart and circulatory health and immune function.
Researched by DoseRoutine R&D TeamReviewed for accuracy by Nicholas Alexander, RSELast updated
Evidence: Moderate — Covered by a systematic review, without regulatory approval.
Evidence strengthModerate · 3/4
PreclinicalStrong human evidence
Covered by a systematic review, without regulatory approval.
Whole-body biological half-life
Not applicable
Typical timing
morning
Food rule
with food
Default unit
iu
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
Reported for Vitamin D2 (Ergocalciferol) in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the Vitamin D2 (Ergocalciferol) entry is written from. Each number matches an inline marker above.
- [1]Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysisTripkovic L, Lambert H, Hart K, et al. · American Journal of Clinical Nutrition · 2012 · Peer-reviewed · PMID 22552031
- [2]Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysisReid IR, Bolland MJ, Grey A · Lancet · 2014 · Peer-reviewed · PMID 24119980
How to track Vitamin D2 (Ergocalciferol) doses
Tracking Vitamin D2 (Ergocalciferol) well takes four fields and a habit. Here is what to record so the log is still useful in three months.
- 1
Add the dose and unit
Log Vitamin D2 (Ergocalciferol) with its dose in iu so totals stay comparable over time — including days when you split the dose or skip it.
- 2
Set the time of day and food rule
Typical timing is morning. Take it with food, and record it that way so absorption stays consistent. Reminders fire at that time and can export to your calendar.
- 3
Check it against the rest of the stack
Run Vitamin D2 (Ergocalciferol) through the interaction checker against everything else in the routine — supplements, peptides, hormones and prescriptions — before it becomes a daily habit.
- 4
Log adherence, not intentions
Mark each dose taken, skipped or delayed as it happens. Weeks of honest logs are what make an adherence rate or a trend line meaningful; retrospective guessing is not.
- 5
Review against outcomes
Review Vitamin D2 (Ergocalciferol) alongside your logged metrics and any relevant blood work every few weeks before changing the dose, so the change is a response to data rather than to a good or bad day.
What to log each time
- Dose in iu
- Time of day and whether it was taken with food
- Taken / skipped / delayed
- Any side effects or notable changes
References & Evidence
Sources on this page that document Vitamin D2 (Ergocalciferol) dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Vitamin D2 (Ergocalciferol) studied for?
Deficiency-driven — not a performance booster
Vitamins primarily help when you're actually low. Extra doses on top of normal levels rarely add strength, endurance, or fat loss, and some fat-soluble vitamins (A, D, E, K) can build up to harmful levels.
- Confirm a deficiency with bloodwork before supplementing long-term (e.g. 25(OH)D for vitamin D, B12/folate, ferritin, magnesium RBC).
- Talk to your doctor or a registered dietitian about the right dose for your labs, medications, and conditions — especially in pregnancy, kidney/liver disease, or while on blood thinners.
- Re-test every 3–6 months and stop or lower the dose once levels are in range.
Educational information only — not medical advice. See our AI & medical policy.
What is Vitamin D2 (Ergocalciferol)?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Vitamin D2, also known as ergocalciferol, is one of two primary forms of vitamin D, the other being vitamin D3 (cholecalciferol). Both D2 and D3 are prohormones that the body converts into calcitriol, the active form of vitamin D. Vitamin D2 is primarily found in plant-based sources like fortified foods (e.g., milk, cereals, orange juice) and some mushrooms exposed to ultraviolet (UV) light. It can also be produced synthetically. The historical discovery of vitamin D was linked to finding a cure for rickets, a bone-softening disease prevalent in children during the early 20th century. Ergocalciferol was identified as the anti-rachitic factor derived from irradiated ergosterol. Its fundamental role in calcium and phosphate homeostasis underscores its importance for bone health and various other physiological processes. (NIH ODS data)
What does the research say about Vitamin D2 (Ergocalciferol)?
Tap a section to expand.
Vitamin D2 is biologically inactive and must undergo a two-step activation process in the body to become its active form, calcitriol (1,25-dihydroxyvitamin D). First, ergocalciferol is metabolized in the liver by the enzyme 25-hydroxylase to form 25-hydroxyvitamin D2, also known as 25(OH)D2 or calcidiol. This compound is the major circulating form of vitamin D and is what is typically measured in blood tests to assess vitamin D status. In the second step, 25-hydroxyvitamin D2 travels to the kidneys, where it is further hydroxylated by the enzyme 1-alpha-hydroxylase to form 1,25-dihydroxyvitamin D2, or calcitriol. Calcitriol then acts as a steroid hormone, binding to the vitamin D receptor (VDR) found in cells throughout the body. This binding initiates a cascade of molecular events that regulate gene expression, primarily impacting calcium and phosphate metabolism. Key actions include: aiding in the absorption of calcium from the intestine, promoting the reabsorption of phosphate by the kidneys, and influencing bone mineralization and remodeling by regulating osteoblast and osteoclast activity. Beyond its well-established role in bone health, vitamin D receptors are present in many other tissues, suggesting broader physiological functions, including modulation of immune function, cell growth, and cardiovascular health. (PubChem data, NIH ODS data)
Source for this section: Sources for How does Vitamin D2 (Ergocalciferol) work?: Jumps to this entry in the sources and references list at the end of the page.
Vitamin D2 contributes to several essential bodily functions. Its primary and most well-understood benefit is its role in maintaining skeletal health. Adequate vitamin D levels are crucial for proper calcium absorption in the intestine and for maintaining appropriate serum calcium and phosphate concentrations, which are vital for bone mineralization. This prevents conditions such as rickets in children and osteomalacia (softening of bones) in adults. It also plays a role in reducing the risk of osteoporosis, a condition characterized by brittle bones, especially when combined with sufficient calcium intake. Beyond bone health, research suggests potential benefits in other areas, though more definitive studies are often needed. These include:
* **Immune System Support:** Vitamin D receptors are found on various immune cells, and vitamin D is implicated in modulating both innate and adaptive immune responses. Some observational studies have linked lower vitamin D levels with increased susceptibility to certain infections and autoimmune conditions. (Cochrane reviews)
* **Muscle Function:** Adequate vitamin D levels are associated with better muscle strength and may reduce the risk of falls in older adults, particularly those who are vitamin D deficient. (Examine.com data)
* **Cardiovascular Health:** Some research explores vitamin D's potential role in cardiovascular health, including its influence on blood pressure and arterial stiffness, though current evidence is not conclusive enough to recommend vitamin D specifically for cardiovascular disease prevention in the general population. (NIH ODS data)
It is important to note that while vitamin D2 can effectively raise serum 25(OH)D levels, some studies suggest that vitamin D3 might be more potent or more efficiently converted to 25(OH)D. However, both forms are considered effective in preventing and treating vitamin D deficiency. (NIH ODS data)
The evidence supporting the efficacy of Vitamin D2 (ergocalciferol) predominantly stems from its established role in preventing and treating vitamin D deficiency, and consequently, bone health disorders. Clinical trials have consistently demonstrated that supplementation with vitamin D2 can effectively increase circulating levels of 25-hydroxyvitamin D, thereby improving calcium absorption and bone mineral density. For instance, studies on children with rickets have shown that vitamin D2 supplementation leads to the healing of bone lesions and restoration of normal bone development. Similarly, in adults with osteomalacia, ergocalciferol has been shown to resolve symptoms and improve bone mineralization. (NIH ODS data, Mayo Clinic data)
Comparative studies examining the efficacy of vitamin D2 versus vitamin D3 in raising serum 25(OH)D levels have yielded mixed results. While some research indicates that vitamin D3 may be more effective or lead to higher and more sustained increases in 25(OH)D concentrations, other studies show comparable efficacy, especially when vitamin D2 is administered at equivalent dosages or in specific populations. For instance, a systematic review and meta-analysis published in the American Journal of Clinical Nutrition concluded that while vitamin D3 might elicit a slightly greater increase, both D2 and D3 are effective in improving vitamin D status. (Cochrane review findings)
Regarding extra-skeletal benefits, the evidence is more varied. Observational studies suggest associations between vitamin D levels and outcomes in areas like immune function, cancer risk, and cardiovascular disease. However, large-scale randomized controlled trials (RCTs) designed to assess the direct impact of vitamin D supplementation on preventing chronic diseases in the general population have often provided inconsistent or null results. For example, some large clinical trials published in journals like *The New England Journal of Medicine* have not found compelling evidence for vitamin D supplementation reducing the incidence of cardiovascular events or cancer in generally healthy individuals. This highlights the complexity of vitamin D's broader physiological roles and the challenges in translating observational associations into definitive clinical recommendations. (NIH ODS data, MedlinePlus data)
Vitamin D2 is generally considered safe when consumed within recommended limits. However, excessively high doses can lead to vitamin D toxicity, a condition known as hypervitaminosis D. This is relatively rare and almost always occurs from over-supplementation rather than dietary intake or sun exposure. Symptoms of vitamin D toxicity are primarily related to hypercalcemia (high blood calcium levels) due to vitamin D's role in calcium absorption and mobilization.
Common side effects associated with hypercalcemia include:
* Nausea and vomiting
* Weakness and fatigue
* Frequent urination (polyuria)
* Excessive thirst (polydipsia)
* Loss of appetite and weight loss
* Constipation
* Confusion, disorientation, or other mental status changes
Chronic hypercalcemia can lead to more serious complications, such as kidney damage, kidney stones, irregular heart rhythms, and bone demineralization (paradoxically, as calcium is pulled from bones to maintain high blood levels). In severe cases, it can be life-threatening.
Less common or mild side effects, typically occurring at modest excess levels, might include headache or metallic taste. It is crucial to monitor vitamin D intake and seek medical attention if any symptoms of toxicity occur. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Individuals with certain medical conditions should exercise caution or avoid vitamin D2 supplementation unless directed and monitored by a healthcare professional. These conditions include:
* **Hypercalcemia:** Individuals who already have high blood calcium levels should avoid vitamin D supplementation, as it can worsen the condition.
* **Hyperparathyroidism:** This condition can lead to naturally elevated calcium levels, and additional vitamin D can exacerbate hypercalcemia.
* **Kidney Disease:** Patients with severe kidney disease may have impaired ability to convert vitamin D to its active form or may be prone to hypercalcemia or hyperphosphatemia, requiring careful medical supervision and possibly specific forms of vitamin D (e.g., calcitriol).
* **Granulomatous Diseases:** Conditions like sarcoidosis, tuberculosis, or lymphoma can cause unregulated production of active vitamin D, leading to hypercalcemia with even normal doses of vitamin D.
* **Arteriosclerosis:** High doses of vitamin D that cause hypercalcemia could potentially worsen calcification in arteries.
* **Allergy:** While rare, some individuals may have an allergic reaction to vitamin D or its inactive ingredients in supplements.
Regular monitoring of blood vitamin D and calcium levels is advisable for individuals taking higher doses or those with pre-existing conditions. Do not exceed recommended dosages without medical guidance. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Vitamin D2 (ergocalciferol) is contraindicated in individuals with known vitamin D toxicity (hypervitaminosis D) and those with malabsorption syndromes who cannot properly absorb fat-soluble vitamins, unless under specific medical supervision targeting the underlying condition. It is also contraindicated in conditions that cause hypercalcemia (high blood calcium levels) or hyperphosphatemia (high blood phosphate levels) *prior* to supplementation, as vitamin D can exacerbate these conditions. Examples include severe arteriosclerosis, elevated blood phosphate, and certain inherited metabolic disorders. Patients with a history of kidney stones should also use caution, as high vitamin D levels, leading to increased calcium absorption, could increase the risk of stone formation. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Several compounds or medications can interact with Vitamin D2, altering its absorption, metabolism, or effects, or intensifying adverse outcomes.
* **Corticosteroids:** These medications, such as prednisone, can reduce calcium absorption and impair vitamin D metabolism. This may necessitate higher vitamin D intake.
* **Orlistat:** This weight-loss medication can reduce the absorption of fat-soluble vitamins, including vitamin D. It's often recommended to take vitamin D supplements at a different time of day or compensate with higher doses.
* **Cholestyramine and Colestipol:** These bile acid sequestrants used to lower cholesterol can also interfere with the absorption of fat-soluble vitamins.
* **Phenobarbital and Phenytoin:** These anticonvulsant medications can increase the metabolism of vitamin D in the liver, potentially leading to lower circulating vitamin D levels and requiring higher supplementation.
* **Thiazide Diuretics:** Medications like hydrochlorothiazide can decrease urinary calcium excretion, which, when combined with vitamin D, can increase the risk of hypercalcemia, especially in susceptible individuals.
* **Digitalis (Digoxin):** Taking vitamin D with digitalis preparations can increase the risk of hypercalcemia, which can, in turn, increase the risk of heart rhythm disturbances in patients taking digitalis. Careful monitoring is essential.
* **Calcium Supplements:** While often taken together for bone health, excessive co-administration of high-dose vitamin D and calcium can increase the risk of hypercalcemia.
* **Other Vitamin D Analogs:** Combining vitamin D2 with other forms of vitamin D or its active metabolites (like calcitriol) without medical supervision can significantly increase the risk of vitamin D toxicity. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Vitamin D2 is a fat-soluble vitamin. As such, it is typically recommended to take it with a meal containing some dietary fat to optimize its absorption. Fatty meals can enhance the bioavailability of vitamin D, as it relies on bile salts for emulsification and absorption in the small intestine. The typical half-life of vitamin D2 is approximately 336 hours, meaning it stays in the body for an extended period. Therefore, consistency in taking it, rather than the exact time of day, is most important. Some individuals prefer taking it in the morning with breakfast to establish a routine. If taking larger, less frequent doses (e.g., weekly or monthly, as sometimes prescribed for deficiency), the timing with food remains relevant for that dose. Individual needs vary — talk to a licensed clinician.
Source for this section: Sources for When should you take Vitamin D2 (Ergocalciferol)?: Jumps to this entry in the sources and references list at the end of the page.
What interacts with Vitamin D2 (Ergocalciferol)?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any vitamin + medication | Note | Category ruleConfidence: theoretical | Certain vitamins interact with specific medications (e.g., vitamin K with blood thinners).Source pending | Specific pairs are checked against a licensed source; confirm with your provider. |
Frequently asked questions about Vitamin D2 (Ergocalciferol)
Vitamin D2 (Ergocalciferol) is a vitamin. It is also known as D2. The references summarized come from NIH and PubMed records, FDA labeling where it exists, and Mayo Clinic patient material.
Vitamin D2 (Ergocalciferol) is commonly discussed in the context of supporting cardiovascular and immune. Individual response varies, and use should be reviewed with a licensed clinician who can weigh the benefits and risks for your situation.
For Vitamin D2 (Ergocalciferol), it is typically taken in the morning and it is usually taken with food. Always follow the specific dose your clinician or the product label prescribes.
Vitamin D2 (Ergocalciferol) carries potential side effects and drug interactions, documented in NIH, Mayo Clinic, and FDA label sources. Stop use and contact a clinician if you experience unexpected symptoms.
As a vitamin, Vitamin D2 (Ergocalciferol) can overlap with other supplements, prescription medicines, hormones and peptides. Because Vitamin D2 (Ergocalciferol) is usually taken in the morning, most avoidable conflicts come from what else lands in that same window. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Vitamin D2 (Ergocalciferol) with no sign-up.
Whether Vitamin D2 (Ergocalciferol) fits alongside testosterone replacement therapy depends on the protocol — dose, ester and ancillaries such as HCG or anastrozole — and on current bloodwork. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
"Peptides" is not one category — healing peptides, GLP-1 agonists, growth-hormone secretagogues and melanocortins each behave differently next to Vitamin D2 (Ergocalciferol). Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for Vitamin D2 (Ergocalciferol) varies by protocol and formulation, so the label or prescription is what sets it. It is typically taken in the morning. Most protocols have it taken with food. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of Vitamin D2 (Ergocalciferol) depends on the protocol and formulation you are on. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Vitamin D2 (Ergocalciferol) the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Which studies looked at Vitamin D2 (Ergocalciferol)?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Clinical uses of 1-alpha-hydroxy-ergocalciferol(opens PubMed in a new tab)Curr Vasc Pharmacol · 2014 · PMID 23713877 · https://pubmed.ncbi.nlm.nih.gov/23713877/
- 2.Effects of Vitamin D2 (Ergocalciferol) on Parathyroid Hormone, Calcium, and Phosphorus in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials(opens PubMed in a new tab)Nutr Rev · 2026 · PMID 40601932 · https://pubmed.ncbi.nlm.nih.gov/40601932/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 5280793(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/5280793
Verify at
Publisher search links for Vitamin D2 (Ergocalciferol). These are places to check the information — they are not citations, so they are not numbered.
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- MedlinePlus(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- Examine.com(publisher search, opens in a new tab)Examine.com · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- DailyMed labeling archive(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Vitamin D2 (Ergocalciferol)?
Plain-text summary, safe to quote verbatim:
Vitamin D2, also known as ergocalciferol, is one of two primary forms of vitamin D, the other being vitamin D3 (cholecalciferol). Both D2 and D3 are prohormones that the body converts into calcitriol, the active form of vitamin D. Research on Vitamin D2 (Ergocalciferol) focuses on heart and circulatory health and immune function.
Source: DoseRoutine — https://doseroutine.com/library/vitamin-d2-ergocalciferol
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Vitamin D2 (Ergocalciferol) — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/vitamin-d2-ergocalciferol
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