Dear Doctor: I am 75 years old, and I donate blood as often as they will accept me. However, I’m often anemic and get rejected. I eat a spinach salad every day, and fish, chicken or beef, plus veggies, for dinner. I’ve been double-dosing on iron supplements, but I’m still anemic. How concerned should I be?

Dear Reader: First, thank you for being a regular blood donor. Thousands of people each day are in need of blood or platelets. These can’t be manufactured and can come only from donors, so volunteers like you are saving lives. According to the Red Cross, the blood and blood products from each blood donation have the potential to save three lives.

In order to protect both the donor and the recipient, each donation is screened for a range of disease markers. The blood is also tested for anemia. Anemia occurs when someone lacks enough hemoglobin to carry adequate amounts of oxygen from the lungs to the tissues throughout the body. Hemoglobin is the protein that makes it possible for oxygen to move from the lungs to the blood, and then from the blood to the tissues.

Mild cases of anemia can be symptom-free. In fact, becoming a blood donor is a common way that people are first made aware of their condition. People with moderate or severe anemia can experience fatigue, breathlessness during even mild exertion, headaches and pale skin, and they can become easily chilled. Without enough red blood cells for their own optimal health, people who are anemic are ruled out as potential blood donors.

With your diet and the use of iron supplements, you’ve taken steps to address iron-deficiency anemia. However, the fact that you continue to be flagged as anemic does raise some concerns.

If you haven’t done so already, we think it would be wise to have a G.I. evaluation. This is to rule out occult bleeding, which is a loss of blood within the gastrointestinal tract that isn’t immediately visible. When you lose blood, you lose iron, which is essential to hemoglobin’s ability to carry oxygen. A common cause of occult bleeding is peptic ulcers, which are sores that develop on the lining of the stomach and the upper part of the small intestine. They can be caused by bacteria or anti-inflammatory drugs. Gastrointestinal bleeding is also a possible side effect of some blood-thinning medications. Occult bleeding may also arise due to inflammatory bowel disease, hemorrhoids, anal fissures, tumors or colon polyps.

Blood from the G.I. tract can usually be detected via a fecal blood test. If the results of a fecal blood test are positive, the next step would be a series of tests that use a scope to examine the upper and lower G.I. tracts to locate and identify the source of the bleed.

In addition to the causes of occult bleeding that we already mentioned, chronic anemia can be a sign of more serious conditions, including immune disorders, long-term infection and certain cancers. We hope that you will work with your doctor to identify the cause of your recurrent anemia.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I read about a family whose little girl got paralyzed by a tick. How does that happen? There are a lot of ticks where we live, and even though we’re careful, somebody gets bitten every summer. Is getting paralyzed something new we have to worry about?

Dear Reader: There’s no denying that ticks are a problem throughout the world. These tiny arachnids, which feed on human and animal blood, are even present in Antarctica, where penguins and nesting seabirds become their hosts.

Although most of the estimated 900 species of ticks worldwide don’t pose a health threat to humans, the handful that do can spread some nasty diseases via their bites. Perhaps the best known of the dozen or so tick-borne illnesses that are most common in the U.S. is Lyme disease, which is transmitted by the blacklegged tick. Many tick-borne diseases are caused by bacteria and can often be treated successfully with antibiotics. But because ticks are so small -- even the minuscule nymphs can cause illness -- and because symptoms often overlap with a range of diagnoses, the challenge often becomes identifying the disease and its source.

Among tick-borne illnesses is tick paralysis. It’s a frightening syndrome that tends to get a lot of media attention whenever a case becomes public. The good news, though, is that, while it’s a concern in livestock, tick paralysis is actually uncommon in humans. When it does occur, it’s seen more often in children than adults. And although tick paralysis is rare, it has the potential to be fatal, so a timely diagnosis is crucial.

The syndrome occurs due to the release of a neurotoxin discharged by the tick’s salivary glands during a bite, most often from a female tick, and usually when she has been attached for several days. And because tick paralysis is chemically induced, removing the tick is the key to reversing the syndrome. When someone from a tick-dense area develops the characteristic symptoms of this syndrome, they should be closely examined for ticks, especially on the scalp and at the hairline, in the armpits, and in the pubic area. In the U.S., the American dog tick and the Rocky Mountain wood tick are the most common cause.

Symptoms begin in the lower extremities and then gradually begin to ascend. They can also include unusual or unexplained fatigue, muscle aches and sensations of tingling and numbness. As paralysis begins to set in, motor control is affected. This causes the person to begin to trip or stumble when they walk. If the attached ticks are not found and removed, paralysis will continue to move upward, affecting the trunk and upper extremities. If it continues unchecked, facial paralysis, which includes the tongue, can occur. In the most extreme cases, convulsions and respiratory failure can lead to death. Within 24 hours of removing the tick, the paralysis typically begins to subside.

Wherever you live, and even if you only go out into the yard, always inspect yourself and your children thoroughly for ticks. Prompt removal can prevent not only tick paralysis, but also other tick-borne diseases.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers, and welcome back for our monthly letters column. Warmer weather is here, so please remember to use sun protection, fend off mosquitoes with bug spray and be aware of ticks as you head outdoors. And now, onward to your questions and comments.

-- After a column about osteoporosis, we heard from a reader dealing with the condition. “I was diagnosed three years ago and tried several medications,” she wrote. “They all had side effects, though, especially on the bowels. What about AlgaeCal?”

The product you’re asking about is a plant-based calcium supplement enhanced with vitamins and minerals. A study published in the Journal of the American College of Nutrition in 2016 found that some people using the product did see an increase in bone density and that the product wasn’t associated with adverse health effects. We encourage you to discuss this option with your health care provider, and also to explore nonbisphosphonate treatments, which are delivered via injection or infusion.

Meanwhile, exercise is an important component of bone health, and we’re glad to know you’ve made it part of your daily routine. In addition to aerobic activities, be sure to include resistance and weight-bearing exercises as well.

-- When discussing the importance of adequate sleep, we have referred to melatonin. A reader wondered about potential side effects. “A couple of years ago, I started taking melatonin before bedtime,” she wrote. “After a few months, I started to feel light-headed and unfocused during the daytime. I stopped taking it, and I started to feel better. Have you ever heard of this before?”

Although melatonin tends to be a benign supplement, it’s efficacy as a sleep aid can vary depending on the dose and the individual. So do side effects, which can include the fuzziness and light-headedness you describe. People have also reported daytime sleepiness, short-term feelings of depression and gastric issues. We’ve had a number of letters about poor sleep (no surprise, considering the year we’ve all just had), so we’ll address nonpharmacologic approaches to insomnia in an upcoming column.

-- A reader had a question in response to a column about bronchiectasis, which is when inflammation and infection cause the bronchial tubes of the lungs to become thickened. “My wife was diagnosed with bronchiectasis in 2007 and had three or four flareups per year that were treated in various ways,” he wrote. “Since being treated with a new medication, she’s had almost no mucus and only one minor flareup in six years. Can bronchiectasis go into remission?”

Yes, the good news is that bronchiectasis can go into remission, which is when the signs and symptoms of a disease are reduced or disappear. However, remission is not a cure. Your wife’s bronchiectasis is under control due to her medications and treatment protocols, so it’s important for her to continue to adhere to them.

Thank you, as always, for your questions and kind comments. We love hearing from you. We continue to get a lot of vaccine questions and will devote a column to them soon.