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Feeling extra fatigued lately? There are lots of reasons why you may not have the usual pep in your step—from overtraining to underfueling to poor sleep habits that are hampering your recovery. But one less obvious factor worth considering: vitamin B12 deficiency.

Most people are not at risk for B12 deficiency, Selvi Rajagopal, M.D., M.P.H., assistant professor of medicine at The Johns Hopkins University School of Medicine, tells Runner’s World. But it’s more common than you may think, especially among seniors. An estimated 20 percent of people over age 60, and about 6 percent of people younger than that are deficient, according to research. 

To make sure you’re filled up on the vitamin, here’s what to know about its benefits, where to find it, and signs of vitamin B12 deficiency to look for, so you know when to talk to your doctor. 

What to Know About the Importance of Vitamin B12

Vitamin B12 plays an essential role in the growth and development of our nervous system tissues and blood cells, Mark Loafman, M.D., a Chicago-based family physician tells Runner’s World. It’s important for nerve signaling and brain functioning, adds Rajagopal. And it helps break down homocysteine, an amino acid that, if present in high enough amounts, can damage the heart and increase risk of dementia, heart disease, stroke, and osteoporosis, Jen Graham, M.S., R.D.N., a Tallahassee, Florida-based registered dietitian nutritionist with Top Nutrition Coaching, tells Runner’s World. 

Our bodies don’t create B12 on their own, so we need to get it from our diet. It’s typically found in animal foods—like meat, eggs, liver, seafood, and dairy products—as well as fortified cereals. 

Because animal products are a main source of this vitamin, folks who follow a strictly vegan or vegetarian diet and don’t take a B12 supplement are at “significant risk” of deficiency, Loafman says. 

Other susceptible people include those who have conditions that interfere with their ability to absorb B12 from the GI tract, including those with celiac disease (and other GI conditions, like inflammatory bowel disease), pernicious anemia (an autoimmune condition), and people who have had bariatric gastric bypass surgery, Loafman explains. 

Older adults, including those older than age 60, are also at risk of deficiency. That’s because the functioning of your gastric cells naturally declines as you age, decreasing absorption of the vitamin, Loafman adds. 

Low levels of B12 are typically detected through a blood test, Rajagopal explains, which you can request from your doctor or may otherwise be included as a part of a routine physical exam. The recommended dietary allowance for B12 ranges from 0.4 to 2.8 mcg per day and varies based on age, sex, and whether you’re pregnant or breastfeeding, according to the National Institutes of Health.

Now that you know the importance of vitamin B12 and who is most affected by deficiency, let’s dig into the signs you’re not getting enough B12—plus how to remedy low levels. 

Signs of Vitamin B12 Deficiency

Having too little vitamin B12 can cause a host of signs and symptoms. These are directly linked to your “body’s inability to keep up with the production of new blood cells and/or the maintenance and preservation of nervous tissues,” Loafman explains. 

Here’s what to watch out for:

Fatigue, weakness, and lightheadedness. B12 deficiency can lead to megaloblastic anemia, a condition where you don’t have enough red blood cells to carry oxygen to your tissues, Rajagopal says. This, in turn, can cause you to feel tired and weak, she explains. It could also hamper your exercise performance, Loafman adds. In severe cases, the lack of red blood cells can be life threatening. The good news: This type of anemia usually occurs gradually and you’d likely notice signs of it with routine blood testing before developing significant symptoms, Loafman explains.

Numbness and tingling in your limbs. These sensations are often symmetric (meaning, they happen on both sides of the body) and typically involve the legs more than the arms, says Rajagopal. It can also crop up in the fingers and toes, she adds. Numbness and tingling happens because B12 deficiency decreases your ability to maintain nervous system tissue, Loafman explains. This effect on the nervous system can also alter your gait and cause difficulty walking.

Mood changes, trouble concentrating, insomnia, irritability, and possible memory loss. When your body isn’t able to maintain its nervous system tissue, it can cause a host of neuropsychiatric symptoms and cognitive dysfunctions, Loafman explains.

Oral irritation and recurrent ulcers. The mucous membranes in your mouth and throat require rapid new cell growth to keep up with the almost constant turnover of cells, so when these areas aren’t getting the new cells they need due to B12 deficiency, your mouth can bear the brunt of it. In addition to oral irritation and frequent ulcers, you may also notice changes to your tongue, including pain, swelling, tenderness, or pigmentation changes, Rajagopal explains.

Skin changes, like rashes and changes in pigmentation. Again, this is because B12 plays a vital role in cell production, Loafman explains, so when your levels are subpar, you may notice it influences your skin health.

GI symptoms, including nausea and diarrhea. Having low levels of B12 can cause fewer red blood cells to reach your digestive tract, which in turn can trigger symptoms like nausea and diarrhea, Graham explains. In turn, feeling nauseous can lower your appetite, she adds.

Irregular heart rate. With B12 deficiency, your heart may beat faster to make up for the reduced number of red blood cells in the body, Graham says. This is your body’s way of trying to ensure enough oxygen gets circulated to all your organs and bodily systems, she explains. 

How to Know if You Need a Vitamin B12 Supplement

If you’re diagnosed with a vitamin B12 deficiency—which, as mentioned, can be determined from a blood test at your doctor’s office—then it’s wise to up your stores by taking a B12 supplement. 

Additionally, anyone who follows a vegan diet should take a B12 supplement to prevent or correct mild deficiencies that may already be developing, Loafman says. He also recommends supplementation for people whose diets include meat or dairy, but focus more heavily on plant-based foods. Important caveat: There are a lot of health benefits associated with solely and largely plant-based diets, “so no one should feel compelled to consume animal products,” Loafman says. Instead, they should add a B12 supplement to their daily routine.

You may also benefit from a B12 supplement if you have an autoimmune disease that attacks the stomach lining or GI tract (like Crohn’s or celiac disease), have had weight-loss surgery, or are taking heartburn medications that suppress stomach acid, Graham says. Your stomach acid is what extracts B12 from the food you eat, so it’s harder for that to happen if you have less stomach acid, she explains. Older adults may also benefit from supplementation, as they are at greater risk of deficiency. 

Just keep in mind: “There is no guideline or strong evidence base to support vitamin B12 supplementation without proven deficiency,” Rajagopal says. So you may want to first get your levels checked and/or ask your doctor if supplementation is recommended for you before taking a daily pill. 

Loafman, for his part, says patients who are struggling with fatigue or other B12 deficiency symptoms often ask him to prescribe supplements or administer B12 injections, even though they don’t have any risk factors for deficiency and a blood test has confirmed their levels are in the normal range. “Often, they have been told or have heard a B12 shot will boost energy levels or help with weight loss,” Loafman explains. “I wish this were the case, but unfortunately there is no evidence of benefit or improved outcome by taking ‘extra’ B12.” 

To that end, if you’re struggling with fatigue, poor performance and/or mood-slash-cognitive concerns, it’s wise to get evaluated by your doctor, Rajagopal advises. They can confirm whether you do have B12 or other micronutrient deficiencies and help you figure out next best steps. 

How to Choose a Quality Vitamin B12 Supplement

If you’ve determined B12 supplementation is right for you, the next step is to get a high-quality product. 

In the United States, vitamins and supplements are not formally regulated, so it’s best to buy supplements that have been tested by an independent third-party company for quality, safety and purity, Graham says. 

Loafman recommends supplements certified by the United States Pharmacopeia (USP) or National Sanitation Foundation (NSF). “I would not purchase or consume an over-the-counter product that does not have this certification,” he says. You can also get a B12 prescription from your physician, which will assure you are getting a product regulated by the Food and Drug Administration, Rajagopal says. 

Look for supplements containing the natural form of B12 (methylcobalamin) instead of the synthetic (cyanocobalamin) because the latter has the potential to impair kidney function in people with borderline kidney problems, Graham says. 

In some cases, B12 injections are recommended over oral supplements. This might be at the beginning of deficiency treatment to obtain faster results, or because your body’s decreased absorption of B12 is so severe that your levels can’t be fixed with high doses of oral treatment, Loafman explains. 

The dosage for your B12 supplement, and which form is right for you, will depend on factors including your specific level of deficiency. Again, this is why it’s worthwhile to first check in with your doctor. 

At 67, Canadian runner Pete Benson is preparing to take on one of the most extraordinary endurance challenges in marathon running: completing seven marathons across seven continents in just seven days while raising money for a cause that reaches far beyond the finish line.

Hailing from Grand Manan, New Brunswick, Benson is set to participate in the Great World Race, an ambitious event that combines the physical demands of marathon running with a demanding journey around the globe. The challenge will require him to complete seven full marathons, each covering 42.195 kilometres, while travelling between continents on a tightly scheduled itinerary.

The challenge is scheduled to begin on November 15, 2026, with pre-event activities expected to start around November 12. Benson's adventure will begin in Antarctica, where the icy terrain and harsh conditions will provide a formidable introduction to the week ahead.

The opening marathon is scheduled for Wolf's Fang in Antarctica, where Benson will face the unfamiliar and potentially unforgiving conditions of the frozen landscape. Reflecting on the prospect of running through the ice and snow, he admitted that the experience is intimidating.

"That's pretty, pretty scary in itself," he said. "Through the ice and snow."

From Antarctica, Benson will travel to Cape Town, South Africa, for his second marathon on November 16. The journey will then continue to Perth, Australia, on November 17, followed by Singapore on November 18. On November 19, he is scheduled to race in the Algarve, Portugal, before heading to Cartagena, Colombia, on November 20. The challenge will conclude in Miami, United States, on November 21.

The demanding itinerary will leave little time for conventional recovery. After each marathon, Benson will need to travel to the next destination, navigate changing time zones and prepare for another 42.195 kilometres. Managing fatigue, nutrition, hydration and sleep will be essential as he attempts to complete the seven races within a single week.

Benson described the unusual routine that awaits him, highlighting the relentless cycle of running and travelling that defines the challenge.

"We run the race, get back on the bus, back on the plane, head to the next one and away we go around the world," Benson said. "That plane becomes our hotel and restaurant for the week, pretty much."

Beyond the physical demands, Benson recognises that taking part in such an ambitious international adventure comes at a considerable financial cost. He describes running as a personal investment, one that has provided him with valuable experiences and opportunities to discover more about himself.

"It's certainly a want, not a need," he said. "Some people go on river cruises and other things that they spend their money on and I spend my money on running and I've learned a lot from it."

Despite the expense, Benson believes the experience is worth the investment.

"So I think the investment is worth it, but it is extravagant," he said.

However, his motivation extends beyond personal achievement. Benson is also using the challenge to raise money for a nonprofit organisation that funds clean-water projects in countries around the world. The fundraising initiative is voluntary and is not a requirement for participating in the event.

By connecting his running adventure to a cause with a tangible impact on communities, Benson hopes to give every kilometre a greater purpose. His effort demonstrates how an individual sporting challenge can also become an opportunity to support work that improves lives.

"I'm happy that there's a purpose behind every mile that I run," he said.

That purpose adds another dimension to Benson's ambitious undertaking. While the seven marathons will test his physical strength, mental resilience and ability to recover between races, his fundraising mission will allow him to contribute to efforts aimed at improving access to clean water around the world.

As November 15 approaches, Benson is preparing for a demanding week that will take him from the ice and snow of Antarctica to the streets of Miami, with five other destinations in between. Each marathon will bring a new test, requiring careful preparation, determination and the ability to keep moving forward despite accumulating fatigue.

At 67, Benson is setting out to complete an extraordinary endurance challenge while supporting a cause beyond himself. Seven marathons, seven continents and seven days will test his limits, but his journey will carry a purpose that extends far beyond the finish line.

Kenyan twins Caroline and Purity Gitonga delivered outstanding performances at the 2026 Valencia Half Marathon in Spain, with both athletes setting new personal bests in a memorable display of endurance, determination, and sibling excellence.

Caroline led the way, clocking an impressive 1:04:59 to finish sixth in the women's race. The performance marked a significant breakthrough for the talented Kenyan, who improved her previous personal best of 1:06:26 by 1 minute and 27 seconds, underlining her continued progress among the world's leading half-marathon runners.

Her twin sister, Purity, was equally impressive, crossing the finish line in 1:05:56 to secure 11th place. She shaved 1 minute and 35 seconds off her previous personal best of 1:07:31, completing a remarkable day for the sisters as they both reached new milestones in their athletic careers.

Their performances highlighted the strength of Kenya's distance-running tradition while showcasing the individual talent and shared determination that have made the Gitonga twins athletes to watch. Competing on one of the world's fastest half-marathon courses, Caroline and Purity demonstrated their ability to translate hard training into significant improvements on the international stage.

Having a twin sister who understands the demands of elite athletics can provide a unique source of motivation. From the discipline required during training to the challenges of competing against the world's best, the sisters share a journey that extends beyond the finish line. Their latest achievements in Valencia offer another inspiring example of how ambition, perseverance, and mutual encouragement can drive athletes toward new heights.

For Caroline, finishing sixth in 1:04:59 represents another important step in her development, while Purity's 1:05:56 performance confirms her own impressive progress. Although they finished several places apart, their achievements tell the same powerful story: two athletes pushing their limits and continuing to improve against a highly competitive international field.

Valencia once again provided a stage for exceptional distance-running performances, and the Gitonga twins made the most of the opportunity. Their personal bests are not only a testament to their hard work but also an encouraging sign of what they could accomplish as they continue to gain experience and pursue even greater ambitions.

Two sisters, two personal bests, and one unforgettable day on the roads of Valencia. Caroline and Purity Gitonga have given Kenyan athletics another reason to celebrate, and their latest performances will undoubtedly strengthen interest in what the talented twins can achieve in the seasons ahead.

Australian endurance athlete Mick Marshall has achieved an extraordinary milestone at the 2026 Marine Corps Marathon in Washington, D.C., setting a world record for the fastest marathon completed on crutches after crossing the finish line in an incredible 5:35:50.

Representing Altra as an elite athlete, Marshall demonstrated remarkable determination and perseverance throughout the 26.2-mile (42.195-kilometre) race, turning one of the world's most celebrated marathon events into a stage for an inspiring display of human resilience.

Completing a marathon is a demanding physical challenge for any athlete, requiring months of preparation, mental strength and the ability to push through fatigue. Covering the same distance on crutches presents a different set of challenges, placing considerable demands on the upper body, coordination and endurance. Marshall's achievement highlights the dedication required to overcome obstacles and pursue goals that many might consider beyond reach.

The Marine Corps Marathon, renowned for its patriotic atmosphere, enthusiastic spectators and scenic course through the nation's capital, provided a memorable setting for the record-breaking performance. As thousands of runners pursued their own finish-line goals, Marshall carved out a special place in the event's history with his remarkable effort.

Beyond the record itself, Marshall's achievement carries a message that resonates far beyond the running community. Every movement toward the finish line required determination, patience and an unwavering commitment to the challenge before him. His performance is a reminder that greatness is not measured solely by how quickly someone reaches a destination, but also by the courage it takes to pursue a goal despite the difficulties along the way. For aspiring athletes and anyone facing personal challenges, his accomplishment offers a powerful lesson in perseverance, self-belief and the importance of refusing to give up when the journey becomes difficult.

His performance also serves as a reminder that marathon running is about far more than finishing times and podium positions. It is a test of courage, commitment and the willingness to redefine personal limits. Marshall's accomplishment demonstrates that the spirit of distance running extends beyond conventional expectations, inspiring athletes and spectators alike to reconsider what is possible through determination and hard work.

Marshall's remarkable run also reinforces the inclusive spirit of distance running, where the finish line belongs to everyone willing to take on the challenge. Whether competing for a championship, chasing a personal best or simply striving to complete the distance, every runner has a story worth celebrating. By setting a world record on crutches at one of America's prominent marathon events, Marshall has added an unforgettable chapter to that story, encouraging others to look beyond perceived limitations and pursue their ambitions with renewed confidence.

For Marshall, the 5:35:50 finish represents more than a time on the clock. It marks an extraordinary personal achievement and a moment that celebrates perseverance, resilience and the determination to keep moving forward. His performance has brought renewed attention to the remarkable possibilities within endurance sport and the many different ways athletes can challenge expectations.

Marshall's achievement at the Marine Corps Marathon stands as a powerful testament to the human spirit, demonstrating that success is not always about having the easiest path, but about finding the strength to keep going. His 5:35:50 performance is a reminder that the finish line can represent much more than the completion of a race: it can symbolise courage, possibility and the extraordinary things people can accomplish when they refuse to give up.

The 23rd edition of the Standard Chartered Nairobi Marathon delivered a spectacular celebration of endurance, determination and competitive excellence on Sunday, October 25, 2026, as Abraham Kiptum and Mercy Kandie Rotich claimed the men's and women's 42km titles in a memorable showcase of Kenyan road-running talent.

With thousands of runners taking to Nairobi's Southern Bypass, the full marathon provided a compelling test of physical strength, tactical discipline and mental resilience. For the elite athletes at the front, every kilometre presented an opportunity to gain an advantage, while the demanding distance required unwavering concentration from the starting gun to the finish line at Uhuru Gardens.

In the men's race, Kiptum produced an impressive performance to secure victory in 2:10:35, narrowly missing the course record by just 23 seconds. The 37-year-old Kenyan demonstrated his experience and endurance throughout the contest, ultimately establishing himself as the strongest performer over the 42.195-kilometre distance.

Kiptum's victory was particularly significant given his recent return to competitive marathon running. The athlete from Kapsabet had continued rebuilding his career and arrived in Nairobi following victory at the CRDB International Marathon in Dar es Salaam, Tanzania, in August. His latest triumph provided another encouraging chapter in his return to the forefront of distance running.

The men's contest produced an exceptionally close battle for the remaining podium positions. Fellow Kenyan Amos Kipkemoi Cheruiyot finished second in 2:10:37, just two seconds behind the champion, while Mark Kibiwott secured third place in 2:11:05.

Dismas Kiplimo finished fourth in 2:11:15, followed by Henry Kiprono Togom, who completed the top five in 2:11:55. The depth of the leading performances underlined the quality of competition on a morning when the front-runners pushed each other towards impressive finishing times.

Kiptum's performance also highlighted the importance of consistency and preparation in marathon running. Having invested months in training, the experienced Kenyan delivered when it mattered most, navigating the course with the composure required to emerge victorious against a competitive field.

The women's 42km race was equally captivating, with Mercy Kandie Rotich claiming the championship in 2:31:25 after a determined performance over the challenging distance.

Rotich demonstrated resilience and composure as the race unfolded, maintaining her challenge through the later stages before securing the victory. Her performance earned her a place among the latest champions of one of Kenya's prominent annual road-running events.

The battle for the women's title was decided by the narrowest of margins. Peris Jerono finished second in 2:31:27, only two seconds behind Rotich, while Ruth Wakabu completed the podium in 2:31:36. The three leading women finished within just 11 seconds of one another, providing a dramatic conclusion to the contest.

Shyline Jepkorir placed fourth in 2:34:55, while Dorothy Kipkilach finished fifth in 2:36:38, rounding out the leading performers in the women's division.

The narrow margins between the leading athletes reflected the unpredictable nature of marathon racing, where pacing, endurance and the ability to respond under pressure can determine the outcome after more than 42 kilometres of competition.

Beyond the podium battles, the full marathon represented a celebration of the determination that defines long-distance running. Every athlete who took on the distance faced the challenge of managing energy, overcoming fatigue and maintaining the mental strength necessary to reach the finish line.

The Southern Bypass provided the setting for these performances, with the runners navigating the Nairobi course before completing their challenge at Uhuru Gardens. The event brought together elite competitors and recreational athletes, united by the ambition to test their limits over the classic marathon distance.

The 2026 edition once again demonstrated the enduring appeal of road racing in Kenya, a country internationally recognised for producing exceptional distance runners. It also offered a platform for athletes to pursue personal ambitions, compete for prestigious honours and showcase the depth of talent within Kenyan athletics.

For Kiptum and Rotich, however, the day belonged to the pursuit of victory. Their respective performances secured them the coveted men's and women's marathon crowns, while the fiercely contested podium finishes ensured that the 42km races delivered the drama and excitement expected of a major road-running championship.

As the 23rd Standard Chartered Nairobi Marathon concluded, the achievements of the two champions stood out as the defining moments of the full-marathon competition, celebrating not only speed and endurance but also the preparation, perseverance and competitive spirit required to conquer 42.195 kilometres.

The true spirit of marathon running was beautifully displayed at the 2026 Mainova Frankfurt Marathon, where the celebration extended far beyond the elite athletes who crossed the finish line first. In a heartwarming tradition, the race's men's and women's champions waited inside the historic Festhalle Frankfurt to welcome the final finisher, reminding the world that every marathon journey deserves recognition.

As the final runner entered the magnificent venue, the atmosphere transformed into an unforgettable celebration. Confetti filled the air as music, dazzling lights and a red-carpet welcome created a moment usually associated with the sport's biggest stars. Standing alongside the champions, the last finisher received a hero's reception, demonstrating that the achievement of completing a marathon deserves to be celebrated regardless of finishing position.

Ethiopia's Jirata Lelisa Dinki, who won the men's race in an impressive 2:05:26, and compatriot Zeineba Yimer Worku, the women's champion in 2:19:45, were among those celebrating the final runner's remarkable achievement.

Their presence sent a powerful message about the values that make marathon running special. While elite athletes push the limits of human performance in pursuit of victory and fast times, thousands of other runners take on the same 42.195-kilometre challenge for deeply personal reasons. For some, the goal is to achieve a personal best; for others, it is to overcome adversity, fulfil a lifelong ambition or simply reach the finish line.

The final finisher's journey may have taken longer than that of the champions, but the determination required to keep moving forward deserves equal admiration. Every kilometre represents effort, sacrifice and perseverance, and crossing the finish line marks the successful completion of a challenge that demands both physical endurance and mental strength.

Frankfurt's special welcome captured an essential truth about distance running: a marathon is not only a race against the clock but also a personal battle against exhaustion, doubt and the temptation to give up. By waiting for the final runner, the champions helped ensure that the day's celebrations included someone whose achievement might otherwise have gone unnoticed.

In a sport often defined by world records, course records and podium finishes, this touching tradition offers a refreshing reminder that the value of a marathon cannot be measured by time alone. The fastest runners may make headlines for their performances, but every finisher has a story worth telling.

At the Mainova Frankfurt Marathon, the champions had already conquered their own challenges. Yet their decision to welcome the last runner created another memorable moment, showing that greatness in sport is measured not only by what athletes accomplish but also by the respect they show others.

Because when the final runner receives the same warmth, applause and celebration as the champions, the message is unmistakable: every runner matters, every finish line represents an achievement, and nobody should be left behind when it is time to celebrate.