There are 21 million transfusions of blood products every two seconds in the United States. And because it's only possible to store blood for a limited time, it's important for Americans to donate their blood on a regular basis.

During winter, the inclement weather, cold and flu season, and the many holiday celebrations put a damper on blood donations, so it's even more important to donate this month. But, according to Study Finds, there are myths that prevent many people from donating blood.

Knowing the truth can prompt more Americans to take the time to give blood and potentially save a life. The American Red Cross helps debunk some of these myths about donating blood:

• It takes too much time. The process takes about an hour and involves three easy steps: registration, a quick health check, and the blood donation. An American Red Cross staff member checks your temperature, pulse, blood pressure, and hemoglobin. The donation takes about eight to 10 minutes, after which you can relax for a few minutes with a drink and snack before leaving.

• It will hurt. It's only the pain of a needle poke, and you shouldn't feel pain after that. "Some of our loyal repeat donors even tell us they've gotten so used to the feeling that they barely notice the needle anymore," says the American Red Cross.

• I have a tattoo, so I can't give blood. In most states, you may give blood immediately after getting a tattoo if you got it in a place that is state regulated. Otherwise, you must wait three months to donate. However, if you got your tattoo in Idaho, Georgia, Maryland, Massachusetts, New Hampshire, New York, Pennsylvania, Utah, Wyoming, or the District of Columbia, you must wait three months, no matter what. Giving blood after piercing with a disposable tool is acceptable, but not if the gun or other instrument used is reusable.

• I don't have a rare blood type, so my blood donation isn't really needed. O negative blood is the universal blood type and can be given to anyone. It's the most common blood type used for transfusions in emergencies when the blood type is unknown and therefore it's almost always the first type to run out during a shortage. Every two seconds someone in the United States needs blood. Every blood type is vital to saving lives.

• I'm too old to donate. People must be older than 16 years to donate blood but there is no upper age limit in the United States. In some states, people can donate blood at the age of 16 with parental consent.

• I'm on medication. In most cases, medications won't interfere with blood donations. However, some medications such as anticoagulants, antiplatelet medication, and even some acne medication may prohibit you from giving blood, says Study Finds. In some instances, there is a wait period after your last dose. Check with your doctor to see if it's safe for you to donate blood. Check out the link Questions About Donating Blood under "Medications" for more information.

• I have high blood pressure, so it's too dangerous for me to donate. It's OK to donate blood if your blood pressure is 180 or below systolic (top number) and 100 or below diastolic (bottom number) at the time of donation. When you donate, a Red Cross staff member will check your blood pressure. Taking medication for high blood pressure doesn't disqualify a donor.

The American Red Cross encourages people to find out more about blood donation and its myths by reviewing its video page. You also can talk to staff members about concerns.