Feeling tired after taking Vitamin D3 can signal you're getting too much (toxicity), causing high calcium (hypercalcemia) with fatigue, nausea, and weakness, or it might be your body adjusting to correcting a deficiency, as Vitamin D impacts sleep-regulating neurotransmitters like serotonin, sometimes causing initial drowsiness or sluggishness before improvement. It's crucial to get your levels tested to differentiate between deficiency correction and overdose, as excessive intake leads to serious symptoms like confusion, dehydration, and kidney stones.
Vitamin D and calcium supplements generally support bone health but can sometimes cause fatigue or digestive issues in some individuals. Taking calcium at night may affect sleep quality or cause mild tiredness. It's important to take these supplements with food to improve absorption and reduce side effects.
Fatigue is a feeling of constant exhaustion, burnout or lack of energy. It can be physical, mental or a combination of both. Fatigue can affect anyone – most adults experience it at some time in their life. Each year, many Australians see their doctor about fatigue.
For pregnancy, the best vitamin D supplement is typically Vitamin D3 (cholecalciferol), as it's more effective at raising blood levels than D2, with studies suggesting higher doses like 4000 IU daily may be needed for sufficiency, though a doctor should guide your specific dosage after a blood test, as too little is risky but excessive amounts (over 100 mcg or 4000 IU) can be harmful.
Vitamin D supplement may have moderate or no effect on the dosage requirement or side effects of pravastatin, rosuvastatin and pitavastatin. Since vitamin D has mild HMG-CoA reductase activity, it will work synergistically with all statins.
Taking vitamin D and statins together can impact cholesterol production and enzyme competition. High doses of vitamin D and digoxin increase the risk of abnormal heart rhythms. Supplements like calcium and magnesium may interact with vitamin D.
Possible interactions include:
The Bottom Line
Vitamin D vs D3, what's the difference? Technically, vitamin D relates to both vitamin D2 (which comes from plants) and vitamin D3 (which the body produces naturally and also comes from animal foods). However, both forms function similarly in the body.
Vitamin D deficiency often has subtle or no symptoms but can cause fatigue, bone pain, muscle weakness/cramps, mood changes (depression), slow wound healing, frequent illness, and hair loss; in children, severe deficiency leads to rickets (bowed bones), while in adults, it increases risks for osteoporosis and fractures.
Vitamin D deficiency affects various body functions including reproductive system in females. Appropriate levels of blood 25-hydroxy vitamin D affect the egg fertility rate, while it does not affect the maturity rate.
Most of the time fatigue can be traced to one or more lifestyle issues, such as poor sleep habits or lack of exercise. Fatigue can be caused by a medicine or linked to depression. Sometimes fatigue is a symptom of an illness that needs treatment.
Fatigue red flags signal potentially serious issues beyond normal tiredness, including unexplained weight loss, persistent fever, night sweats, shortness of breath, chest pain, severe headaches, confusion, or new neurological/joint problems alongside exhaustion. Other signs include fatigue worsening with activity, significant cognitive/mood changes, or lack of energy despite rest, suggesting conditions like infection, autoimmune disease, heart problems, cancer, or mental health issues, warranting prompt medical evaluation.
But pushing through when your body is telling you to rest can actually do more harm than good. “If you regularly ignore signs of physical fatigue and train without proper recovery, you could put yourself at risk of overtraining,” Whitehorn says. Overtraining syndrome is a real concern.
Common Low Vitamin D Symptoms
Fatigue and exhaustion: This is one of the most common complaints. You might feel persistent tiredness that doesn't improve with rest. Even simple tasks feel draining. Bone and muscle pain: Aching bones, muscle weakness, or generalized body pain often signal low vitamin D.
Vitamin D deficiency causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults. Vitamin D deficiency has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases.
Taking too much vitamin D leads to calcium buildup (hypercalcemia), causing physical signs like nausea/vomiting, fatigue/weakness, frequent urination & excessive thirst, constipation, and confusion/disorientation, alongside potential bone pain or kidney stones, often from supplements, not sun exposure.
“Adding an over-the-counter vitamin D supplement can make improvements in just three to four months. Vitamin D with a strength of 1000-2000 international units daily is the recommended dose for most adults,” Dr. Ropte says.
Vitamin D absorption can be prevented by limited sun exposure (dark skin, sunscreen, covering up, indoor lifestyle), medical conditions (celiac, Crohn's, cystic fibrosis, liver/kidney disease, obesity), certain medications (steroids, anti-seizure drugs, weight-loss drugs), and even some nutritional factors like low magnesium, with fat malabsorption issues and obesity being major culprits for preventing both dietary and sun-derived vitamin D from working effectively.
You should not use cholecalciferol if you have had an allergic reaction to vitamin D, or if you have: high levels of vitamin D in your body (hypervitaminosis D); high levels of calcium in your blood (hypercalcemia); or. any condition that makes it hard for your body to absorb nutrients from food (malabsorption).
1,25-dihydroxyvitamin D3 and its receptor, the VDR, have several biological functions in skin, including regulating the proliferation and differentiation of keratinocytes, hair follicle cycling, and tumor suppression.
This meta-analysis of 20 RCTs demonstrated that vitamin D supplementation significantly alleviates depressive symptoms, with an overall standardized mean difference (SMD) of -0.36 (95% CI: -0.52 to -0.20, p < 0.00001), supporting its role as a viable adjunctive therapy for depression.
The two most common mistakes when taking vitamin D are taking it without adequate fatty foods for absorption, and neglecting to take it with Vitamin K2 and magnesium, which are crucial for directing calcium to bones and activating the vitamin D in your body, respectively, leading to ineffective supplementation or calcium buildup issues. Many also mistakenly choose the less effective D2 form over D3, or take incorrect dosages without blood tests, according to this snippet from Healthshots, this snippet from GrassrootsHealth, this snippet from Yahoo! Health, this snippet from the Cleveland Clinic Journal of Medicine, and this snippet from Verywell Mind.
The best sources are the flesh of fatty fish and fish liver oils. Smaller amounts are found in egg yolks, cheese, and beef liver. Certain mushrooms contain some vitamin D2; in addition some commercially sold mushrooms contain higher amounts of D2 due to intentionally being exposed to high amounts of ultraviolet light.
About 50% of people worldwide have low vitamin D levels. And between 10% and 30% of the population are thought to have low levels of magnesium. For many people, it's important to take vitamin D and magnesium together. Without magnesium, your body can't use vitamin D.