A vitamin D deficiency means you don't have enough vitamin D in your body. Too little of vitamin D makes bones weak. But the link between vitamin D and blood pressure isn't clear.

Vitamin D may change how some body chemicals control blood pressure. The vitamin also seems to keep the lining of blood vessels flexible and healthy. If you have low vitamin D, your arteries can become stiff. This makes it harder for blood to flow.

Research about vitamin D and heart health has been mixed. Here's what studies say so far:

• A low vitamin D level seems to increase the risk of heart disease and death due to heart disease.
• Too little vitamin D level may make you more likely to have high blood pressure and diabetes. These conditions increase the risk of heart disease.
• It's not clear whether taking a vitamin D supplement every day protects against heart attacks and strokes. It may only help those with extremely low vitamin D levels.

Still, vitamin D is needed for overall good health. Here are the recommended daily amounts from the National Academies of Sciences, Engineering, and Medicine:

• Adults ages 19 to 70 should get 600 international units (IU) of vitamin D a day.
• Adults over 70 should try to get 800 IU a day.

Remember, more of a vitamin isn't always better. Do not take more than 4,000 IU a day.

If you're worried about your vitamin D level, talk with your healthcare team. A blood test can be done to check your vitamin D level.

Screening for vitamin D deficiency is especially important in those with brown or Black skin. Darker skin has higher levels of a natural substance called melanin. The more melanin you have, the harder it is for your skin to make vitamin D from the sun.

Others who may benefit from having their vitamin D level checked are:

• People who don't spend a lot of time in the sun.
• Older adults.
• People with some health conditions that make it hard to absorb vitamin D.