Lying down. Eating snacks. Saving lives.

Really, what's not to like about giving blood?

After all, you have something inside you that no factory can make, and that a lot of people need in order to survive. You can give it safely, in about an hour, and you'll barely feel a thing.

Did I mention the snacks? They're free. So are the friendly smiles of the blood drive staff and volunteers (you can really tell they're smiling through their masks.)

Also free? The feeling that you're helping your fellow humans, though you'll never know exactly which ones.

I've been donating blood for decades, a few times a year, even through the pandemic (and yes, even after all three of my COVID vaccine doses.)

I've even got a pin to prove that I've given five gallons of my blood, which works out to about 40 donations.

So I've collected some of my favorite insider tips about donating blood.

If you've never given blood, or you did it long ago but stopped, this is a great time to start. There's actually a shortage of blood right now, and blood banks are pulling out all the stops to bring in more donations before people get busy during the holiday season.

Take, for instance, the Blood Battle between the University of Michigan and Ohio State University. It's a contest to see which school can bring in the most blood donors in the month before the football rivals meet on the field.

I'm proud to say I scored a point for U-M this week by giving at a drive on campus. There are plenty of blood donation appointments still open before the competition ends November 24.

Why should you give blood?

Just a few miles away from the U-M stadium sits the main campus of U-M's Michigan Medicine. The patients who come to our hospitals and clinics need an incredible amount of blood every day.

The Blood Bank director, pathology professor Robertson Davenport, M.D., leads a team that works closely with the Red Cross to make sure we have enough blood, platelets and plasma to treat patients for everything from cancer and sickle cell disease to heart surgery, liver failure and severe car crash injuries.

Even some COVID-19 patients get blood products, especially those on the life-support system called ECMO.

MORE FROM MICHIGAN: Sign up for our weekly newsletter

"Michigan Medicine uses about 32,000 units of red blood cells, 15,000 units of platelets, and 7,000 units of plasma annually," Davenport told me. "Major clinical services that rely on blood transfusion include heart surgery, including coronary artery bypass surgery and heart valve repair; cancer care such as leukemia and bone marrow transplantation; congenital heart surgery for infants and children born with heart defects; transplant surgery to replace failing livers, lungs and hearts; and emergency services for trauma and acute bleeding."

He cited just a few recent examples of patients who needed a large amount of blood:

• A teen girl born with a heart defect who developed an infection and needed more heart surgery.

• A middle-aged man who needed a second lung transplant after his first transplant failed.

• A young man with a history of leukemia who received a bone marrow transplant but suffered acute bleeding.

• A young woman who came to the emergency department with acute intestinal bleeding.

• An older man with acute leukemia and an infection that he couldn't fight off.

• A middle-aged man who received a new liver to replace his failing one.

Tips for a successful blood donation

1. First, figure out if you're eligible to donate blood

It's true, the Red Cross and other blood-gathering agencies don't take just anyone's blood. They must make sure it's safe for donors to give, and safe for the recipients to get.

Still, while about 38% of Americans meet all the criteria to give blood, only 10% actually do it. That's why shortages happen.

So it's time to check the blood donation eligibility guidelines if you're assuming you won't qualify, or if you didn't qualify in the past because of a tattoo or piercing you got, a trip you took, or a medicine you were taking. Guidelines have changed!

If you're a member of the LGBTQ+ community, see the special page for you (and note that the U.S. Food and Drug Administration is working with the Red Cross to evaluate potential changes to its donation guidelines for gay and bisexual men.)

If you've recently gotten vaccinated against COVID-19, with a first, second or third dose of any of the vaccines approved for use in the U.S. or Canada, you don't have to wait before donating blood. The waiting period was removed earlier this year. You also don't have to wait after getting a flu shot or most other vaccinations (check the eligibility criteria to be sure.)

If you've recently had COVID-19, you need to wait until you're a few weeks after your positive test or symptoms before donating.

SEE ALSO: Feeling Helpless as the Pandemic Continues? 26 Things You Can Do to Help

One of the eligibility criteria that has tripped me up from time to time is the level of hemoglobin in my blood, which relates to levels of iron. In fact, this is pretty common, especially for women, and the Red Cross offers information about why it's important and what you can do.

Each donor gets a rapid hemoglobin test as part of the pre-donation process, but you don't want to make the trip to a donation site only to find out your level is too low.

So, I take an iron supplement and a vitamin C supplement to help my body absorb the extra iron, and I try to eat iron-rich foods in the weeks before a donation. If you think you might have low iron, talk to your health care provider about whether you should take a supplement.

Like Podcasts? Add the Michigan Medicine News Break on iTunes, Google Podcasts or anywhere you listen to podcasts.

2. Pick your day and time, and "pregame" a few days before you give blood

The Red Cross has an easy-to-use online scheduling system that lets you find a blood donation time and location that's convenient for you (you may live in an area served by another blood-gathering organization, but they likely have one too.)

Most donations take about an hour from start to finish, but with COVID precautions and staff shortages this can stretch out a bit longer at peak times. So don't book a donation time that starts an hour before a crucial meeting or when you have to pick someone up.

Pro tips for feeling your best when giving blood:

• I try to pick donation times after lunch, so I can have a meal about half an hour to an hour before I arrive. This gets sugar into my bloodstream so I'll be less likely to feel woozy after I give. But no matter what time you give, make sure to have at least a snack before you go.

• The day before your appointment, you'll get an email nudging you to take care of the pre-donation questionnaire and get a digital Rapid Pass that will speed your way through the donation process. This just takes a few minutes and includes important information about eligibility that might be specific to your area (such as whether you were informed you ate at a local restaurant associated with a hepatitis A outbreak).

• This tip is crucial: Start drinking extra water a few days before your appointment. Getting fully hydrated will plump up your veins and make your donation go more smoothly.

• By the day of your appointment, you should be so well-hydrated that your urine is nearly colorless and you find yourself needing bathroom breaks more often than usual. Also, avoid coffee, tea, cola or other caffeine-containing drinks and foods on the day of your appointment, since they make your body get rid of water faster.

• Plan your outfit: Short sleeves, or sleeves you can unbutton and roll to above your elbow, are a must. You can wear a sweater or jacket before and after you donate. Don't wear a skirt or dress because it's not easy to get on and off the high donation cot in one. (I found that out the hard way. Never again!) Super-tight jeans or waistbands aren't a great idea either.

3. Know what to expect at your donation:

If you want a great detailed explanation of what happens at a blood donation appointment, the Red Cross offers a full blow-by-blow.

Check out the list below for a quick run-down of what you can expect along the way.

Blood donation preparation checklist:

• Bring your ID, so they can make sure you're you. If you have a donor card from a past donation, bring it, too.

• Wear a mask. Blood donation drives are health care settings, so it's likely required, though that could change depending on local COVID case rates.

• Bring your smartphone or something to read in case you have a bit of a wait.

• If you didn't do the Rapid Pass in advance, be ready to go over all the eligibility questions about your health and travel history, and other topics, on the computer of the staff member assigned to you.

• Even if you did do the Rapid Pass, you will still have a few more questions to answer. Be honest about everything they ask – they will keep the information confidential.

• If you're with a friend and get deferred from donating because of how you answered a question, but you don't want to tell the friend the reason, you can say it was low iron or something.

• If you're concerned you might have low iron, ask them to test your hemoglobin first before you invest too much time in the appointment. This involves a pinprick on one of your fingertips to get a drop of blood. If your level is too low on the first try, they can test it one more time from a different finger.

• You'll get your temperature, pulse and blood pressure taken – so basically, giving blood includes a free health screening!

• Remember to keep your feet flat on the floor, your body relaxed and your breathing calm when they take your blood pressure.

• If you're anxious about needles, use distraction to keep yourself from worrying. Enjoy the sound system that's playing upbeat music. Trade stories or crack jokes with the staff (they have a long day on their feet). Do some patterned breathing. And tell the staff that you're not a fan of needles so they can help you through the process.

• They'll ask you which arm you want to give from. Some people prefer to try to give from their non-dominant arm, but honestly there is no pain afterward so it should not matter. And sometimes the easier-to-access veins are on your dominant arm, so using it might make things go more smoothly to use that one.

What it's like to donate blood, step by step:

• The staff will put a blood pressure cuff on you and narrate every step of the process, from using a marker to outline the vein they'll use, to cleaning your skin to prevent infection, to inserting the needle and telling you when to squeeze or roll the soft roller or squishy ball they'll put in your hand.  

• The needle goes in on the inside of your elbow, and staff are excellent about doing it as quickly and painlessly as possible. Thankfully there really aren't many nerve endings in that spot, so it's more like a moment of discomfort than pain. 

• Once you've started the actual donation, you'll be surprised at how quickly it goes – 15 minutes or so depending on the size of the vein and how hydrated you are. You need to keep rolling that object in your hand to keep the blood flowing. You can read something on your smartphone in your other hand to pass the time.

• A key tip: Don't talk or laugh much while you're actually donating; this will deplete the oxygen in your blood and make you more likely to get woozy when you're done and you sit up.

• They'll stop your donation after they've collected about 500 milliliters of blood, which is about 2 1/3 cups. Since your body has about 1.5 gallons of blood, this is an absolutely safe amount to take.

• Most of the blood goes into a bag, but before you're done they will also collect small amounts in a few vials, for testing.

• When you're done, they'll take the needle out painlessly, put gauze over the needle site, and have you press on it and elevate your arm to accelerate the clotting off of the insertion point. Then they'll put a bandage on it and use red gauze wrap to hold it in place. Wear that red wrap with pride for the next hour or so! Keep the bandage in place a while longer.

• If you're squeamish about seeing your own blood in the collection bag, don't worry – it hangs down the side of the cot while you're giving, and once they've clamped it off and laid it on the cot, you can easily pivot out of the way once you sit up and not ever see it.

• Listen to the instructions they give you about avoiding alcohol or caffeine that day, as well as lifting heavy things or exercising. There's a reason for these instructions! Consider this a free pass to take it easy for the rest of the day – but be sure to keep drinking water to replace the fluids you've lost.

• Keep the paper they give you, which has a unique bar code specific to you and a number you can call if you develop any symptoms. For instance, if a cold or COVID-like symptoms start the day after you donated, you need to tell them right away so they don't give your blood to someone who might be much more vulnerable to those infections.

• If you feel faint or not quite right, tell them. You can sit on your cot a bit longer, or go to the recovery cot near the snack area.

That's it!

Now you can enjoy those snacks and juices that the nice volunteer will offer you in the recovery area. Don't feel greedy if you want a second helping.

Sitting at the snack table for 15 minutes, with both your feet on the floor, is important to making sure you're OK before going back to your day. It also gives time for some of the sugar from the snack and juice get into your bloodstream.

And when you do leave, pat yourself on the back. You just gave enough blood to save up to three lives.

You can even trace the journey of your donated blood through the Red Cross app, and get an alert about which hospital it ended up at after testing and processing.

And while you're on the app, make your next donation appointment, for at least two months from now, or longer if your iron levels were on the low side.

And that's how you can keep the cycle of giving blood – and saving lives – going.