Study Finds Link Between Low Iron and Long COVID

A small new study shows that there might be a link between long COVID and low iron levels.

Researchers at the University of Cambridge recruited 214 people who tested positive for COVID-19 for the study, gathering blood samples over the course of a year. The patients ranged from not having any COVID symptoms to being sick enough to be hospitalized. The researchers tracked any symptoms that the patients developed and noted symptoms that lasted beyond the initial COVID infection.

About 45% of the participants had symptoms of long COVID between three and 10 months after they originally had the virus. Study participants whose bodies took a longer time to regulate inflammation and iron levels, as well as those who had more severe initial infections, had a higher risk of developing long COVID.

The researchers also discovered that the bodies of people who developed long COVID had more problems regulating iron levels, which was noticeable as soon as two weeks after they had COVID-19.

Helping people with symptoms of long COVID has been a major goal for researchers, with about 7% of American adults saying they’ve had long COVID and a quarter of adults with the condition having significant activity limitations. The new study raises questions about whether iron levels could play a role and if supplementation could help.

Iron and Illness

While the study’s authors did not determine why they saw a link between low iron levels and long COVID, experts have a few theories.

“All creatures need iron to survive, including microbes, and microbes that cause infections need to acquire iron from us,” Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, told Verywell.

When you get an infection like COVID, your body decreases iron absorption and shifts its availability so it’s withheld from the microbes making you sick, according to Russo.

“This is part of the pro-inflammatory response that occurs due to infection,” Russo said. If your body has chronic inflammation, you can develop anemia—a condition where your body does not have enough healthy red blood cells.

When you have low levels of iron in your blood, it makes it harder for oxygen to be transported to the organs and tissues that need it, lead study author Aimee L. Hanson, PhD, a senior research associate in Genetic Epidemiology at the University of Bristol, told Verywell.

“Reduced oxygen delivery to muscles during exertion can lead to muscle fatigue, pain, and decreased physical endurance,” she said. “Similarly, low oxygen levels in the brain have been linked to cognitive impairment—‘brain fog’—and altered mood.”

Hanson noted that “all of these consequences are also reported symptoms of long COVID.”

Plus, when tissues don’t have enough oxygen, it can take longer for the body to heal. Iron is also used by cells in the body for energy production, so a lack of iron can “severely inhibit” the basic function of cells, according to Hanson. People with low iron often feel fatigued, and may even be susceptible to more infections and have longer recovery times when they do get sick.

Should You Take an Iron Supplement If You Have COVID?

While it’s not clear if having low iron levels before catching COVID raises the risk of long COVID, Hanson said it’s possible.

“We may predict that having lower baseline levels of iron exacerbates the physiological consequences of the anemia that develops during infection, making it even harder for the body to re-establish an equilibrium in the following weeks to months,” she said. “This is one potential explanation for the increased prevalence of long-COVID in pre-menopausal women, a group in which iron deficiency is more common.”

How—or even if—iron could be beneficial for people with COVID is “speculation right now,” according to Russo, who also noted that it’s unclear if targeting the inflammatory response to a COVID infection would help. It’s also not clear whether there would be any benefit to taking supplemental iron.

Controlled clinical trials are needed to find out.

“There is possibly a window of time post-infection in which bolstering [blood] iron levels will be most beneficial to support immune function and recovery,” Hansen said. “The method by which this is achieved has to be carefully tested.”

Inflammation during and after an infection also directly affects the body’s ability to absorb iron or reuse iron from cells that store it. That interference might reduce the efficacy of dietary iron supplements after COVID, Hanson said. In that case, IV iron might be more helpful.

How Much Iron Do You Need?

The recommended daily allowance (RDA) of iron is a bit different depending on a person’s sex, age, and whether they menstruate. The RDA is 8 milligrams a day for adult men and 18 mg for adult women under the age of 50.

Pregnancy raises the RDA to 27 mg a day, and breastfeeding lowers it to 9 mg a day. Once women reach age 51, the RDA drops to 8 mg a day. Infants, young children, teens, pregnant people, and premenopausal people are the most at risk for having low iron.

If you’re wondering if those recommendations would change if you got COVID or had symptoms of long COVID, the short answer is that we don’t know.

It’s not clear what the iron level threshold would increase the risk of long COVID.

“Relative to the healthy control included in our study cohort, those hospitalized with COVID-19 had, on average, half to one-quarter of the concentration of iron detectable in [blood] in the first two weeks of disease,” said Hanson.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.