Vitamin B12 and vitamin D are two important substances that support multiple functions in your body. Deficiencies in either of these vitamins can impact your overall health.
Vitamin B12, which most humans get from meat, seafood, and dairy products, is essential for red blood cell production and DNA synthesis. It also supports nervous system health and functionality, and it helps protect and repair damaged nerves.
Vitamin D, which humans absorb through UV rays or get from a few foods, such as fish oils, supports the immune system and fights inflammation. It’s also vital for mental health. Most importantly, vitamin D helps the body absorb calcium, which is necessary for bone growth. Most supplements contain either vitamin D2 or vitamin D3.
Both these vitamins are common in supplements in both oral and injectable forms. You might wonder if taking both together brings additional benefits, or if it could cause side effects.
Here’s a closer look at the effect vitamins D and B12 have on each other if you take them at the same time.
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The Benefits of Taking Vitamin D and B12 Together
Vitamin D and B12 have different functions in the body, but there is some overlap. For instance, vitamin B12 supports the nervous system, while vitamin D affects mood functions in the brain. Both also play a role in immune system health.
At least one study found that both vitamins can work together to help brain development and health throughout your lifetime. The research, published in the medical journal Nutrients, found that B12 and D, taken with folic acid, can reverse memory problems caused by a vitamin D deficiency. This approach may be especially useful for people with early signs of Alzheimer’s disease.
Overall, both vitamins promote general health, meaning both should be a part of your dietary considerations or supplementation plans.
Potential Side Effects and Interactions
Vitamin D and B12 do not interact negatively with one another. However, you don’t get the maximum benefits by taking them together with your biggest meal of the day.
Research has shown that vitamin D absorption is heightened if you take it with a large meal. This timing can increase serum levels of beneficial compounds by as much as 50%.
Vitamin B12 typically requires different timing. The best B12 absorption occurs at least two hours after eating and 30 minutes or more before you eat again. This applies to tablets or other oral supplements. It does not matter for B12 injections, which bypass the digestion process and directly enter the bloodstream.
Symptoms of Combined Vitamin D and Vitamin B12 Deficiency
Vitamin D and B12 deficiencies can occur independently. Some symptoms of low levels of each vitamin are unique, but there are a few signs that overlap. For instance, deficiencies in both could cause fatigue, but nerve pain was unique to B12, and bone pain was associated with a D deficiency.
Deficiencies could also cause mental health issues. B12 affects brain and nervous system functions, and a deficiency can cause clinical depression. A concurrent vitamin D deficiency can increase the severity of mental health problems.
Recommended Dosages and Forms
Vitamin D and B12 deficiencies can cause serious symptoms. A proper diet and adequate sunlight may help maintain vitamin levels in the long term, but supplementation is often necessary. It can either involve oral supplements or injections.
Oral Supplements
Oral supplements, available as tablets, capsules, lozenges, and other edible forms, have several important advantages. The most obvious is that they are easy to take, and you can keep a large supply in your home for daily use.
The recommended daily allowance for vitamin B12 is 2.4 mcg for adults. However, vitamins may contain higher doses of 50 to 500 mcg and 1,000 to 2,000 mcg tablets are available. These higher dosages are typically for treating deficiencies rather than for ongoing maintenance.
Children and adults need 15 mcg of vitamin D; the dose is sometimes written as 600 IU (International Units). Those over 70 may need 20 mcg (800 IU). Higher doses might be necessary to treat deficiencies.
While oral supplements are convenient, they have drawbacks. Absorption or gastrointestinal issues can limit the amount that gets into your bloodstream. Also, taking oral supplements at the wrong time can limit their effectiveness. For instance, you need to take vitamin D at meal times, but taking B12 with food can limit the amount that reaches your bloodstream.
Injections
People commonly use B12 injections to treat deficiencies. One of the primary benefits is that the shot puts the full dose of B12 into the bloodstream. None gets lost to absorption or digestive tract issues, which can limit the effectiveness of oral vitamins.
Injections may seem more inconvenient. However, you can learn to administer the shot yourself so that you do not have to go to the physician each time you need a dose.
B12 injection doses can range from 100 mcg to 1,000 mcg, depending on the person, their age, and their condition. Multiple doses are common at the start of treatment, with monthly maintenance injections afterward.
Therapeutic doses of vitamin D can differ based on the same variables, but 50,000 IU (1,250 mcg) is a common amount according to the journal Nutrients.
Personalizing Your Vitamin Intake
Since both B12 and D are available through dietary sources, you can benefit from personalizing your nutrient plans. For instance, if you suffer from a B12 deficiency, you can add oily fish, organ meat, beef, and fortified cereals to your diet to maximize your intake without supplementation.
You can then incorporate supplements into your diet to meet any needs not covered by the foods on your plate.
You can also consider intermittent B12 injections. You might explore options that combine B12 with other beneficial elements. For instance, you might look at liver-protecting lipotropic compounds with B12.
Incorporating Vitamins Into Your Diet
What foods can ensure you have sufficient B12 and D in your diet? The following dishes are high in B12:
- Beef liver
- Shellfish
- Salmon
- Tuna
- Ground beef
Dairy foods like milk, yogurt, and cheese can also work toward your daily B12 needs. Fortified plant-based foods and beverages may also contain B12.
Dietary sources for vitamin D are more limited. However, there are some seafood options and fortified foods. These include:
- Salmon
- Freshwater trout
- Sardines
- Mushrooms
- Fortified milk
Sunshine is the best source of vitamin D. When it’s sunny, you can get as much as 10,000 IU of vitamin D in a single day.
The Role of Lifestyle in Vitamin Absorption
Lifestyle choices can affect how your body handles nutrients. For instance, alcohol inhibits nutrient absorption, especially for B vitamins. Also, restrictive diets, such as vegan diets, can complicate dietary vitamin intake. Both B12 and D are primarily from meat, seafood, and dairy. Vegans who do not pay careful attention to fortified food intake may be at risk for a deficiency.
When To Take Vitamin D and B12
Oral vitamin D is best absorbed when taken alongside food, and oral B12 works better on an empty stomach. This means you’ll need to take oral supplements at different times. However, taking them together isn’t likely to bring any negative side effects.
The timing for vitamin injections can vary depending on the purpose of the supplementation. For instance, doctors may treat a B12 deficiency with several shots in the first month, followed by monthly or quarterly injections for maintenance.
Signs of Overdose and What To Do
You won’t overdose on dietary vitamin B12 or D. Also, most supplements are well below the upper limit. However, high doses, such as those used to treat serious deficiencies, can cause symptoms.
A B12 overdose might trigger nausea or diarrhea. It can also cause rashes, anxiety, nerve twitching, or heart palpitations. Unless you experience swelling or trouble breathing, you can usually flush the excess vitamins out of your system with water. In severe cases, a doctor can administer saline through an IV.
Vitamin D toxicity can also cause gastrointestinal distress, and it can lead to a buildup of calcium that can lead to bone and kidney pain. Very high doses can cause kidney damage. Hydration and IVs can help in mild or moderate cases. Dialysis may be necessary if you develop severe kidney problems.
You can safely take vitamins B12 and D together. However, you need to be aware of potential side effects if you take large doses of either one of these substances.
