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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. 

Jakob Ingebrigtsen brought his remarkable 2026 season to a fitting close on home soil, winning the men’s street 1500m at the inaugural Runfest Norway in Sandnes on Friday.

Competing in front of an enthusiastic hometown crowd, the Olympic and world champion took control of the race from the early stages and maintained his authority through the finish, stopping the clock at 3:40.7.

Andreas Fjeld Halvorsen followed in second in 3:43.3, while Sigurd Tveit completed the podium in 3:47.8.

The unusual street race added another dimension to the occasion, with 273 runners taking part on the same road and sharing the course with one of Norway’s most accomplished distance runners. For the recreational participants, it offered a rare opportunity to compete alongside Ingebrigtsen in an event that brought elite athletics and mass participation together.

The victory also provided a fitting final chapter to a season that began with significant uncertainty for Ingebrigtsen. After undergoing major Achilles surgery in February, the Norwegian was forced to miss a substantial portion of the summer campaign as he worked his way back to full fitness.

His return, however, quickly developed into another championship-winning chapter. In Birmingham, Ingebrigtsen captured European 5,000m gold before adding another major title at the inaugural World Athletics Ultimate Championship in Budapest, where he won the 5,000m.

Those performances transformed what could have been a disrupted season into another year defined by championship success and a determined return to the highest level.

Now, with the Sandnes victory added to his 2026 record, Ingebrigtsen closes the year exactly where it began in spirit — overcoming adversity, rebuilding his form and once again competing at the front.

From Achilles surgery in February to major championship victories and finally a 1500m win before his hometown crowd, the Norwegian has given his 2026 season a memorable final scene.

Olympic 100m hurdles champion Masai Russell has announced her engagement to longtime partner Robert “Robbie” Springfield, adding a major personal milestone to the remarkable journey of one of America’s leading track and field stars.

Russell shared the news with her followers, revealing that Springfield had proposed and that she had accepted. Reflecting on their relationship, the Olympic champion described him as her best friend and expressed her excitement about spending the rest of her life with him.

The couple’s relationship dates back to their college years at the University of Kentucky, where both were student-athletes and competed in track and field. Russell established herself as a standout hurdler, while Springfield competed in the long jump, giving them a shared understanding of the demands, sacrifices and pressures that come with pursuing success in athletics.

Springfield has since transitioned from competition into coaching. A former collegiate long jumper, he is now part of the coaching staff at Morehead State University, where he works with the programme’s sprinters and jumpers.

Their relationship has developed alongside Russell’s rise to the top of the sport. The defining moment of her career came at the Paris 2024 Olympic Games, where she captured gold in the women’s 100m hurdles, securing her place among the sport’s Olympic champions.

Away from competition, Springfield has remained a familiar part of Russell’s journey, sharing in the demanding periods of training and competition that accompanied her pursuit of Olympic success. Their connection has consequently grown from a college athletics relationship into a long-term partnership.

The engagement now marks another significant chapter for Russell, this time away from the track. After reaching the pinnacle of her sporting career in Paris, the 100m hurdles champion is beginning a new phase of her personal life alongside a partner who has been part of her journey since their university days.

From competing on the same collegiate stage to building a future together, Russell and Springfield’s story has evolved alongside two careers shaped by track and field. The Olympic champion will now balance this new personal chapter with her continuing ambitions in athletics

The women’s race at the 2026 TCS Amsterdam Marathon is shaping up to be one of the most competitive editions in recent years, with a deep international field set to take on the fast Dutch course on Sunday, October 18.

At the centre of the contest will be four Ethiopian athletes who have already broken the 2:20 barrier, creating the prospect of a fascinating battle for victory and a possible assault on the course record of 2:16:52.

Defending champion Aynalem Desta will return to Amsterdam looking to retain her title after producing the biggest performance of her career at last year’s 50th edition. Desta won in a personal best of 2:17:37, establishing herself among the leading marathoners in the field and setting the benchmark for this year’s contenders.

Standing in her way will be fellow Ethiopian Meseret Belete Tola, a former Amsterdam champion who knows exactly what it takes to succeed on the course. Belete Tola captured the 2023 edition in 2:18:21, and her return adds another layer of experience and proven quality to an already formidable lineup.

The field also includes Mestawut Fikir Truneh, who arrives with an impressive marathon pedigree. Truneh finished runner-up at the 2024 Berlin Marathon in 2:18:48, demonstrating her ability to compete at the highest level on one of the world's major marathon stages.

Completing the quartet of sub-2:20 Ethiopians is Buze Diriba, whose personal best of 2:19:34 places her firmly among the leading contenders. With four athletes possessing credentials below 2:20, the race is likely to develop into a tightly contested battle from the opening kilometres.

The depth extends well beyond the leading quartet. Desi Jisa Mokonin, representing Bahrain, Yeshi Kalayu Chekole of Ethiopia and Nazret Weldu Gebrehiwet of Eritrea have all established themselves as serious marathon competitors with performances approaching the 2:20 mark.

Another major name to watch is Abeba Aregawi, the former 1500m world champion representing Sweden. Aregawi has successfully transferred her talents to the marathon and made headlines earlier this year by setting a Swedish national record of 2:23:12 on her debut. Her presence adds another intriguing dimension to an already high-quality field.

Amsterdam’s marathon course has consistently provided an opportunity for elite athletes to produce fast times, and this year’s women’s lineup has the depth to turn the race into a genuine test of both championship racing and outright speed.

With four athletes already inside 2:20, two former Amsterdam champions returning to the start line and several other accomplished marathoners ready to challenge them, the battle is expected to remain open deep into the race.

The ultimate target will be the Amsterdam women’s course record of 2:16:52. Whether the leading contenders can threaten that mark remains to be seen, but the quality assembled for October 18 ensures that the record will be firmly in the spotlight when the race reaches its spectacular finish inside the Olympic Stadium.

The 2026 Valencia Half Marathon is shaping up to be a thrilling contest of speed, endurance and tactical brilliance, with some of the world’s finest road runners set to converge in Spain on October 25.

Kenya’s Daniel Ebenyo and Alex Matata will be among the leading contenders, facing a formidable Ethiopian challenge spearheaded by Jemal Yimer and Tadese Worku. The field also features Rodrigue Kwizera, who boasts the fastest personal best among the leading entrants at 58:16.

Ebenyo arrives with a personal best of 59:04, placing him firmly among the athletes capable of sustaining a demanding pace over the 21.1-kilometre distance. Matata, who owns a 59:11 best, adds further Kenyan strength, while Andrea Kiptoo brings another sub-60-minute credential to the race.

Yimer has already established himself as one of the fastest athletes in the field with a 58:33 personal best, while Worku has clocked 58:35. Kenya’s Owen Korir, with a best of 58:58, further underlines the remarkable depth of the men's lineup.

Valencia Half Marathon 2026 Entries

1. Rodrigue Kwizera (Spain) — 58:16

2. Jemal Yimer (Ethiopia) — 58:33

3. Tadese Worku (Ethiopia) — 58:35

4. Owen Korir (Kenya) — 58:58

5. Daniel Ebenyo (Kenya) — 59:04

6. Alex Matata (Kenya) — 59:11

7. Andrea Kiptoo (Kenya) — 59:11

8. Thierry Ndikumwenayo (Spain) — 59:42

9. Said Mechaal (Spain) — 1:00:24

10. Adel Mechaal (Spain) — 1:02:30

Kwizera, who finished second in Valencia last year, leads the field on paper and will be seeking another standout performance on the famously fast Valencia course. With several athletes carrying sub-60-minute credentials, the race has the ingredients for an aggressive battle from the opening kilometres.

Beyond the headline names, the men’s field is deep and highly competitive, bringing together a strong collection of experienced international athletes with proven ability over the half-marathon distance. With so much quality packed into the lineup, the race promises an intriguing battle in which tactics, endurance, positioning and finishing speed could all play a crucial role in determining the eventual champion.

Yet personal bests will count for little once the gun goes off. The title could ultimately be decided by patience, positioning and the ability to respond when the pace begins to rise in the closing stages. Every surge, every tactical move and every second saved could prove decisive on the road to the finish.

With Kenya, Ethiopia and Spain represented by athletes of exceptional quality, Valencia promises a high-octane men's showdown in which the leaders are likely to be separated by only a handful of seconds. The final kilometres could provide the defining moments of a race packed with speed, ambition and anticipation.

On October 25, the question will be simple: who has the strength to command the streets of Valencia and claim the coveted half-marathon crown?

 

April 19, 1982. The Boston Marathon unfolded under unusually warm, sunny conditions, and by the closing stages, the race had become a private battle between two very different American runners: Alberto Salazar, already one of the biggest names in distance running, and Dick Beardsley, the Minnesota runner who had emerged as a serious marathon contender.

For roughly nine miles, from the Newton Hills toward the finish, Beardsley did much of the leading, with Salazar tucked close behind. Neither man could shake the other. They ran deep into Boston locked together, trading surges and refusing to surrender an inch as the crowds along the course grew louder.

Salazar finally made his decisive move with less than a mile remaining. He opened a small gap, but Beardsley refused to disappear. The Minnesota runner chased him through the final streets, closing again as they approached the finish.

Then came the final sprint.

Salazar held his form and reached the finish first in 2:08:52, with Beardsley only two seconds behind in 2:08:54. It was an extraordinary result: both men broke 2:09 in the same Boston Marathon, and both shattered the previous course record.

The race became known as the “Duel in the Sun,” and it remains one of the most celebrated head-to-head battles in Boston Marathon history. Beardsley had not won, but his performance established him as one of America's elite marathoners.

For Salazar, however, victory came at an enormous physical cost. Immediately after crossing the finish line, he collapsed and required emergency treatment, including several litres of intravenous saline. The combination of heat, dehydration and an all-out effort had pushed his body to the limit.

Salazar's marathon career would never again produce quite the same kind of performance. His celebrated 1981 New York City Marathon victory had produced what was initially considered a world record, although the course was later found to be short. His Boston triumph therefore became one of the defining victories of his career.

Beardsley's story would take an even more difficult turn. Injuries disrupted his career, and after returning to the highest level, he suffered a devastating farm accident in 1989. Further accidents, surgeries and severe physical pain followed, eventually leading to a long battle with painkiller addiction.

He eventually overcame that struggle and transformed the darkest chapters of his life into a story of recovery, resilience and redemption.

That is what makes the 1982 Boston Marathon more than a two-second victory.

For one extraordinary afternoon, Salazar and Beardsley produced a marathon duel in which neither man was willing to give way. One crossed the finish line first. The other finished only two seconds behind him.

Two seconds separated them at Boston. Decades later, their legendary duel remains one of the greatest chapters in marathon history.