How Soon Will I Feel Better After Taking Vitamin D?


So, you are low on sunshine vitamin1 and wondering how soon you feel better after taking vitamin D. The answer to this differs for everyone. Typically, people with really low vitamin D levels will wait a longer time than people who need a top-up, before they start feeling better.

About vitamin D

Vitamin D, a fat-soluble vitamin is an important nutrient needed by the body to help build and maintain strong bones. It helps our body absorb glucose and also helps in the absorption of calcium,2 which is a nutrient that makes up the bone. Vitamin D also controls many other cellular functions in the body by supporting immune health, brain cell activity and muscle function through its anti-inflammatory and antioxidant properties, and by protecting the nervous system.3

Vitamin D is a unique vitamin because it can be made in the skin after exposure to the sun when the sunlight converts cholesterol in the skin to calciferol, an active form of Vitamin D. This is the sole reason it is called the sunshine vitamin. 

The amount of vitamin D the skin makes is dependent on many factors, like your skin colour and what time of day, season or latitude it is. Vitamin D production might reduce or be completely absent depending on your lifestyle and where you live. 

Importance of vitamin D 

Vitamin D promotes the absorption of calcium in the intestine and maintains sufficient serum calcium and phosphate concentrations to enable normal bone hardening and to prevent involuntary spasms and cramps from muscle shrinkage, known as hypocalcemic tetany. It is also needed by osteoblasts, which form bones, and osteoclasts, which remove bones,  for bone growth and bone repair.4

Not having enough vitamin D in your body can cause your bones to become fragile,  thin, or deformed. Vitamin D helps to prevent rickets in children or adults, osteomalacia - soft bones. In conjunction with calcium, vitamin D also helps protect older adults from osteoporosis; a disease where the bone becomes so fragile it breaks easily from things such as a fall or even minor stresses like coughing or bending over.

You have sufficient Vitamin D when your Vitamin D level is 30 to 32 ng/mL. Maintenance of a 30 to 32 ng/mL level requires approximately 2,200 to 3,000 IU/d of vitamin D from all sources, including ultraviolet light exposure, food, and supplements.

Deficiency of vitamin D

Vitamin D deficiency has been said to be a global health pandemic. About 1 billion people worldwide have vitamin D deficiency, while 50% of the population has vitamin D insufficiency.6 You are said to have a deficiency of Vitamin D when your serum level is below 20 ng/ml, with 

Vitamin D insufficiency being between 20 ng/ml to 29 ng/ml.2

You can develop vitamin D deficiency when your usual intakes of Vitamin D are lower than the recommended levels. This is also the case when you have limited exposure to sunlight as in the case of indoor workers or people in places where the sun doesn’t shine so intensely (areas far from the equator)7, your kidneys cannot convert calciferol to calcitriol,  its active form, or your body can not adequately absorb vitamin D from your intestines. Vitamin D deficiency is also common in people who are lactose intolerant, have a milk allergy or people who are on a vegan diet or are ovo-vegetarians.

Vitamin D deficiency can increase the risk of some autoimmune diseases including multiple sclerosis, type 1 Diabetes, lupus, and psoriasis.2

Symptoms of vitamin D deficiency

If you have been severely deficient you can experience symptoms like fatigue, muscle twitching, bone pain, joint pain (especially in the wrists, ankles, shins and shoulders), muscle pain, depression, hair loss and weakness.2 Symptoms of Vitamin D deficiency in children include; drowsiness and disinterest, irritability, dental problems, delay in development, bone fractures or bone changes.6

Test to identify the deficiency of vitamin D 

To identify the deficiency of vitamin D, the 25 Hydroxyvitamin D test is carried out. This test, also known as the  calcidiol 25-hydroxycholecalciferol test or 25-OH vitamin D test,  measures the level of Vitamin D in your blood.

The desired range for this test varies according to demographics although anything between 20-50 ng/ml is accepted.8

You have a mild vitamin D deficiency when your 25-hydroxyvitamin D is below 20 ng/mL, moderately deficient when it is below 10 ng/mL and severely deficient when it is below 5 ng/mL.  However, serum levels above 100 ng/mL, can lead to Vitamin D toxicity which leads to a buildup of calcium in the blood. Mayo Clinic9 lists the symptoms of toxicity as weakness, frequent urination, nausea and vomiting. If not treated, by discontinuing supplements, Vitamin D toxicity may cause bone pain or go on to affect the kidneys by the formation of calcium stones in the kidney.

Treatment options

After the test has been carried out, and you are diagnosed with Vitamin D deficiency, your healthcare provider will likely prescribe oral Vitamin D supplements, in the form of Vitamin D3 or Vitamin D2,  because only a few foods can provide the adequate amount of Vitamin D you need. In rare cases, administering injections through the muscle might be a treatment option; as in the case of  people with liver disease, gastrectomy or whose intestines are not able to absorb vitamin D.

How can I increase the levels of vitamin D?

Regular multivitamins contain approximately 400 IU (International Unit) of vitamin D, although currently, some other multivitamins contain between 800 to 1000 IU. The amount of supplement you need is largely dependent on your age, how low your vitamin D levels are and your risk factors6. There are a variety of options available for vitamin D supplements, they come as chewable tablets, capsules, drops, and liquids.  

Cod liver oil is also a good source of vitamin D. A teaspoon of cod liver oil contains 450 IU of Vitamin D  as well as Vitamin A and omega-3 fatty acids. In large doses, the cod liver may present a risk of vitamin A toxicity.

How long does it take to increase the levels of vitamin D?

According to the American Society of Clinical Oncology,2 each daily intake of 1,000 IU of vitamin D3 together with an increase in foods rich in Vitamin D will raise the level of 25-Hydroxyvitamin D by 10 ng/mL after a few weeks. Note that the dosage may be increased for individuals who are obese, due to vitamin D being fat soluble. It can be hidden in body fat and may not be utilised before its 2 or 3 weeks of availability in the body.

Other vitamin D rich sources 

Other than exposure to the UVB rays of the sun, some foods such as fish and shellfish provide some amount of natural vitamin D (oily fish are best). An egg yolk will provide about 20 IU but care should be taken because of its high cholesterol content. Other foods like Vitamin D-fortified low-fat milk, yoghurt, some orange juices, and certain oatmeals and cereals will, in a serving, provide about 100 IU of the Recommended Dietary Allowance (RDA) of 400-800IU.

Mushrooms (both the regular type and those exposed to UVB), cheese,  beef liver, sardines, salmon, tuna, herring and pickled herring are good sources of Vitamin D. The National Institutes for Health has a list4 of other foods with their IU.

Ways to help avoid vitamin D deficiency

The skin absorbs about 50% to 90% of vitamin D from the sun while the body gets the remaining from the foods we eat. Having over 40% of your skin exposed to while out in the sun for at least Twenty minutes daily will help to avoid vitamin D deficiency.6

Eating superfoods rich in Vitamin D and sun exposure goes a long way in helping prevent Vitamin D deficiency. It is good practice to keep an eye on your vitamin D levels to ensure you do not get critically deficient without knowing, especially if you are at risk of deficiency.

Before getting started on Vitamin D supplements; if you do not get enough sun exposure, are allergic to dairy, are on a vegan diet or feel that you have insufficient Vitamin D, speak to your healthcare provider who may test and/or prescribe the right supplement for you. People taking some drugs such as drugs for convulsion, drugs containing aluminium, and steroids, are not supposed to take vitamin D because it may cause an adverse effect.3

How to safely get Vitamin D from the sun

The time of day when you are exposed to sunlight is of importance as this determines the amount of UVB present to produce Vitamin D in the skin. The best time to absorb the maximal amounts of UVB is at noon, when the sun is directly above, although in countries such as the United Kingdom, even at midday from October to March, UVB is insufficient to produce a generous amount of vitamin D.10 

In other countries, at noon, the sun is intense and may cause harm to the skin if sunscreen was not used before exposure to the sun. Sunscreen is best applied 10-30 minutes before your exposure to sunlight and it works to protect the skin from the damaging rays of the sun which can cause sunburn, premature ageing of the skin, eye problems, heat stroke and skin cancer. 

There is an ongoing debate on whether the use of sunscreen reduces how much Vitamin D the body absorbs after sun exposure.11, 12


Although Vitamin D is an important nutrient that helps maintain body functions, improve mental health, aid in the formation and regulation of bones, and help improve overall well-being, it can cause adverse effects when taken in excess. You do not have to take another dose if you do not start feeling better after taking your supplement because the duration before you start feeling the effect is dependent on many factors, including how severe your Vitamin D deficiency is.

Knowing what foods contain Vitamin D as well as their IU, in addition to  adequate exposure to sunlight will help to avoid Vitamin D deficiency. 


  1. Nair, Dr Rathish. “Vitamin D: The Sunshine Vitamin.” Journal of Pharmacology & Pharmacotherapeutics, Jan. 2012.,
  2. Khan, Qamar J., and Carol J. Fabian. “How I Treat Vitamin D Deficiency.” Journal of Oncology Practice, vol. 6, no. 2, Mar. 2010, pp. 97–101. (Atypon),
  3. “Vitamin D.” Mayo Clinic, Accessed 2 Aug. 2022.
  4. Office of Dietary Supplements - Vitamin D. Accessed 2 Aug. 2022.
  5. “Osteoporosis - Symptoms and Causes.” Mayo Clinic, Accessed 2 Aug. 2022.
  6. Sizar, Omeed, et al. “Vitamin D Deficiency.” StatPearls, StatPearls Publishing, 2022. PubMed,
  7. Sowah, Daniel, et al. “Vitamin D Levels and Deficiency with Different Occupations: A Systematic Review.” BMC Public Health, vol. 17, no. 1, June 2017, p. 519. BioMed Central,
  8. Bilezikian, John P., et al. “Vitamin D: Dosing, Levels, Form, and Route of Administration: Does One Approach Fit All?” Reviews in Endocrine and Metabolic Disorders, vol. 22, no. 4, Dec. 2021, pp. 1201–18. Springer Link,
  9. “Vitamin D Toxicity: What If You Get Too Much?” Mayo Clinic, Accessed 2 Aug. 2022.
  10. Rhodes, Lesley E., et al. “Recommended Summer Sunlight Exposure Levels Can Produce Sufficient (≥20ngml−1) but Not the Proposed Optimal (≥32ngml−1) 25(OH)D Levels at UK Latitudes.” Journal of Investigative Dermatology, vol. 130, no. 5, May 2010, pp. 1411–18.,
  11. Passeron, T., et al. “Sunscreen Photoprotection and Vitamin D Status.” British Journal of Dermatology, vol. 181, no. 5, Nov. 2019, pp. 916–31. (Crossref),
  12. Neale, R. E., et al. “The Effect of Sunscreen on Vitamin D: A Review.” British Journal of Dermatology, vol. 181, no. 5, Nov. 2019, pp. 907–15. (Crossref),
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Chimezirim Ozonyiri

Bachelor of Science - BS, Microbiology, General, Tansian University, Nigeria

Chimezirim has several years of experience in the healthcare, non-profit, and education sectors. She is passionate about health promotion and began her journey into health and lifestyle writing over two years ago.

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