Ashley Harwyn, PA-C, ABAAHP | Published August 4, 2025 | Last updated October 6, 2026 | 21 min read
Fatigue, ice cravings, tingling feet, and slow-healing cuts can point to low iron, B12, magnesium, or zinc. Here is what each sign may mean and which test actually tells you.
Food comes first in our nutrition coaching, and a blood test is how a deficiency gets checked.
For adults in Charleston and Mount Pleasant who feel off and wonder whether nutrition is part of it, ten signs worth raising are feeling tired more often than usual, getting winded easily, craving ice, restless legs at night, brittle nails or hair loss, a sore tongue, tingling in the hands or feet, trouble concentrating, muscle cramps, and wounds that heal slowly. Each one appears on a MedlinePlus symptom list for low iron, vitamin B12, magnesium, or zinc, and several appear on more than one list, so the honest next step is a test, not a guess.[1][2][4][6] If a test confirms a gap, our nutritional therapy service offers personalized nutrition coaching built from your labs, symptoms, and routine.
This guide walks through the ten signs one at a time: what each one may mean, which lab checks it, who is more likely to run low, and why buying supplements on a hunch can cause its own problems. It is written for adults who want a straight answer about whether nutrition is part of the story. Where the evidence is thin, we say so.
Key takeaways
Mild iron deficiency anemia may cause no symptoms. When symptoms do show up, they are often mild at first and develop slowly, and may include tiredness, headaches, dizziness, and problems concentrating.[1]
Low vitamin B12 that goes on for a long time can damage nerves, causing numbness, tingling, and balance problems, and that damage may be permanent if treatment does not start promptly.[2]
A symptom is a reason to test, not a diagnosis. Tests named by MedlinePlus include a complete blood count, ferritin for iron stores, serum B12 and methylmalonic acid, and a blood magnesium level.[1][2][3][4]
Vitamin D is not one of the ten. It helps the body absorb calcium, which is needed for normal bone formation, and the US Preventive Services Task Force found the evidence insufficient to judge routine vitamin D screening in adults without symptoms.[7][8]
The FDA does not approve dietary supplements before they are sold, and biotin, often found in supplements, can interfere with certain lab tests.[9][10]
Blood or a black, tar-like look in your stool is a reason to contact a clinician, because bleeding can cause iron loss.[1]
Section 01 / Iron clues
Signs 1 to 4: could you be running low on iron?
Your red blood cells use iron to build hemoglobin, the protein that carries oxygen. Without enough iron to make hemoglobin, your blood cannot carry oxygen as well, and the first four signs on this list are symptoms MedlinePlus ties to low iron.[1]
1. Feeling tired or weak more often than usual. Fatigue is the vaguest sign on this list. MedlinePlus lists feeling weak or tired more often than usual, or with exercise, among the symptoms of iron deficiency anemia, along with headaches and dizziness.[1] Low vitamin B12 can cause fatigue and a lack of energy too, and low magnesium lists fatigue among its common symptoms.[2][4] MedlinePlus even lists weakness or fatigue as a symptom of iron levels that are too high, which is why tiredness alone tells us to look, not what we will find.[3]
2. Getting winded on the stairs, or a heart that pounds. Palpitations are on the early symptom list for iron deficiency anemia, and shortness of breath and feeling lightheaded when you stand up may appear as it gets worse.[1] Vitamin B12 deficiency can do the same, with shortness of breath mostly during exercise and lightheadedness on standing or exertion.[2] MedlinePlus lists shortness of breath, dizziness, pale skin, and arrhythmia, a problem with the rate or rhythm of the heartbeat, among the symptoms of low iron that may prompt a ferritin test.[3] Call 911 for new chest pain or fainting.
3. Craving ice, or things that are not food. A strong desire to eat ice or other non-food things has a name, pica, and MedlinePlus lists it as a symptom that can appear as iron deficiency anemia worsens.[1] It is worth mentioning even if it feels odd to say out loud. If you also have heavy, long, or frequent periods, say so too, because MedlinePlus lists them among the common causes of bleeding that can lead to iron loss.[1]
4. Legs that will not settle at night. MedlinePlus describes restless legs syndrome as a tingling or burning feeling in the legs that may be caused by a lack of iron.[3] It includes uncontrolled leg movement during sleep among iron deficiency anemia symptoms, and lists restless legs syndrome as one of the conditions a ferritin test can help diagnose or rule out.[1][3] If your legs keep you up, ask whether a ferritin test makes sense for you.
Who tends to land here? Bleeding causes iron loss, and heavy, long, or frequent menstrual periods are a common cause of that bleeding. Pregnancy and breastfeeding raise iron needs. Celiac disease, Crohn disease, and gastric bypass surgery can keep the body from absorbing enough iron, and long-term use of aspirin, ibuprofen, or medicines that thin the blood can cause bleeding in the gut.[1] MedlinePlus also lists being a strict vegetarian among the reasons a diet may not supply enough iron.[1]
Section 02 / Visible clues
Signs 5 to 7: what can your nails, hair, mouth, and skin show?
Some of these signs show up where you can see them. These three are easy to notice in a mirror, so treat them as prompts to ask, not proof.
5. Brittle nails or hair loss. Brittle nails and hair loss both appear on the MedlinePlus list of symptoms that can develop as iron deficiency anemia gets worse.[1] Loss of hair is also listed among the symptoms of zinc deficiency.[6] Because hair loss shows up on both lists, it points to a question rather than an answer. If hormones are a likely factor, our guide to early signs of hormonal imbalance in women covers that side.
6. A sore, red, or swollen tongue, or mouth ulcers. A sore or inflamed tongue and mouth ulcers can come with iron deficiency anemia.[1] A swollen, red tongue or bleeding gums can come with vitamin B12 deficiency.[2] Point them out at a visit, even when the main complaint is fatigue.
7. Cuts that heal slowly, frequent infections, or food that tastes off. Zinc is needed for the immune system to work properly and for the senses of taste and smell, and it plays a role in wound healing. MedlinePlus lists frequent infections, wounds that take a long time to heal, skin sores, poor appetite, and problems with taste or smell among the symptoms of zinc deficiency.[6] Low-protein and vegetarian diets tend to run low in zinc, because the zinc in plant foods is not as available to the body as the zinc from animal sources.[6] One caution belongs right here: a long-term excess intake of zinc can lead to copper, iron, or magnesium deficiency, so more is not better.[6]
Section 03 / Nerves and muscles
Signs 8 to 10: what do nerves, focus, and muscles have to do with nutrition?
The last three signs involve the nerves and the muscles. They matter because MedlinePlus warns that nerve damage from a long-term vitamin B12 deficiency may be permanent if treatment does not start promptly.[2]
8. Numbness, tingling, or unsteady balance. Your body needs vitamin B12 to make red blood cells. When B12 stays low for a long time, it can cause nerve damage, with numbness and tingling of the hands and feet and loss of balance.[2] MedlinePlus is direct about the stakes: that damage may be permanent if treatment does not start promptly after symptoms begin.[2] Low magnesium can also cause numbness.[4] Because numbness appears on both the B12 and the magnesium lists, testing is how the two get told apart.
9. Trouble concentrating, irritability, or confusion. Problems concentrating or thinking show up on the early symptom list for iron deficiency anemia.[1] With vitamin B12, feeling irritable is listed, and problems concentrating appear among the symptoms of nerve damage from a long-term deficiency, with confusion or a change in mental status in severe cases.[2] That does not mean a B12 pill sharpens a healthy memory. MedlinePlus states there is no evidence that taking B12 supplements will prevent or treat dementia or Alzheimer disease.[2] The goal is to find and fix a true deficiency, not to supplement past it.
10. Muscle cramps, twitching, or a fluttering heartbeat. Muscle spasms or cramps, muscle weakness, and fatigue are common symptoms of low magnesium.[4] MedlinePlus lists muscle cramps, numbness or tingling, and an irregular heartbeat among the symptoms of low magnesium that may lead to a magnesium blood test.[5] Common causes include alcohol use, chronic diarrhea, excessive urination such as in uncontrolled diabetes, malabsorption problems such as celiac disease, and medicines such as diuretics and proton pump inhibitors.[4] When magnesium drops too much, it can be a life-threatening emergency, and MedlinePlus advises contacting your provider right away if you have symptoms.[4]
Recognize several of these signs? Call 843-981-0870 to book a visit, and bring your symptom notes and a full list of every medicine and supplement you take.
Section 04 / Lab confirmation
Which blood tests confirm a nutrient deficiency?
A sign gets you in the door. A lab result tells you what is actually going on. The tests below are the ones MedlinePlus describes for each deficiency, and none of the MedlinePlus pages cited here treat a single symptom as proof of a deficiency; each lists tests to confirm it.[1][2][3][4]
Source: US Preventive Services Task Force, Vitamin D Deficiency in Adults: Screening (2021), and MedlinePlus, Vitamin D. A number on its own is not a diagnosis; it is read with your history.
Sign you notice
Nutrient it may point to
Test that checks it
Keep in mind
Tiredness, getting winded, pale skin
Iron or vitamin B12
Complete blood count (CBC) and reticulocyte count[1][2]
A CBC can show anemia; other tests sort out the cause
Ice craving, restless legs, brittle nails
Iron
Ferritin, serum iron, and total iron binding capacity[1][3]
Ferritin reflects how much iron your body has stored[3]
Screening adults without symptoms: evidence insufficient[8]
Bring this to your visit
Which of these apply to you?
Tap any that fit. This does not diagnose anything. It flags details that help decide which labs make sense and what to ask about.
A few plain readings of that table. First, a complete blood count is a starting point. It can show that you are anemic, but MedlinePlus lists separate tests, like ferritin for iron or methylmalonic acid for B12, to check the cause.[1][2] Second, a ferritin result shows stored iron, which is why it can be used to check for low iron before symptoms develop in people at high risk, such as those with heavy menstrual bleeding, pregnancy, or trouble absorbing food.[3] Ferritin can also flag the opposite problem, hemochromatosis, which means too much iron in the body, and MedlinePlus warns that too little or too much iron can cause serious health problems if not treated.[3]
Third, magnesium is tricky to read. Most of the body's magnesium is stored in bones, organs, and other tissue, and only a small amount is in the blood, which the kidneys and intestines tightly control.[5] The normal blood range MedlinePlus gives is 1.6 to 2.6 mg/dL, though ranges may vary slightly among labs, and it advises talking with your provider about what your specific result means.[4]
Fourth, vitamin D. The best measure of vitamin D status is a blood level of 25-hydroxyvitamin D. MedlinePlus says levels below 12 to 20 ng/mL are too low for bone or overall health, levels of 20 ng/mL or above are enough for most people, and levels above 50 ng/mL are probably too high.[7]
National survey data from 2011 to 2014 cited by the USPSTF found 5 percent of people age 1 and older had very low levels, under 12 ng/mL, and 18 percent had levels between 12 and 19 ng/mL.[8] Yet the Task Force concluded the evidence is insufficient to weigh the benefits and harms of screening adults who have no symptoms.[8] So it is fair to ask whether you have a specific reason to test. MedlinePlus notes that risk factors for osteoporosis, or a disease that reduces vitamin D absorption, can change how much vitamin D a provider recommends.[7]
If you are due for a broader checkup anyway, our annual full panel labs include a complete blood count, a metabolic panel, and nutrient levels, with the exact list tailored to your age, history, and risk factors.
Test, find the cause, then treat
A sign prompts a targeted blood test. If a deficiency is confirmed, treatment is matched to it, the reason for it is looked for (bleeding, absorption, medicines, diet), and the level is rechecked.
Guess, then supplement
Buying a pill for a symptom skips the test, can leave the cause (such as bleeding) unexamined, can distort some lab results (biotin), and long-term excess zinc or too much vitamin D carries its own risks.
Section 05 / Higher risk
Who is more likely to run low on these nutrients?
Some people are more likely to come up short. MedlinePlus notes that a ferritin test can check for low iron before symptoms develop in people at high risk.[3] None of these groups are guaranteed a deficiency.
Heavy or frequent periods, pregnancy, or breastfeeding. Blood loss drains iron, and pregnancy and breastfeeding raise the body's iron needs.[1]
Plant-based eating. MedlinePlus lists a strict vegetarian diet as a reason for low iron and low vitamin B12, and vegetarian diets tend to be lower in zinc.[1][2][6]
Long-term heartburn medicine or metformin. Taking antacids and other heartburn medicines for a long time, or long-term metformin for blood sugar, can make it harder to absorb B12.[2] Proton pump inhibitors, which reduce stomach acid, are also on the list of medicines linked to low magnesium.[4][5]
Gut conditions or gut surgery. Celiac disease, Crohn disease, and weight-loss surgeries that remove or bypass part of the stomach or small intestine can reduce absorption of iron and B12.[1][2] If digestion itself is the main complaint, read our guide to signs your gut needs attention and consider our gut health care.
Alcohol use. Alcohol is listed as a cause of low B12 and of low magnesium.[2][4]
Diuretics or chronic diarrhea. Both are listed among the causes of low magnesium.[4]
Notice how many of these come down to medicines and medical conditions rather than willpower or a “bad diet.” That is a good reason to bring your full medication and supplement list to any visit about these symptoms. A heartburn pill taken for years and tingling feet can look unrelated, yet MedlinePlus links long-term heartburn medicine to trouble absorbing B12, so it is worth asking whether your B12 should be checked.[2]
Section 06 / Supplement cautions
Why can guessing with supplements backfire?
When people suspect a deficiency, the usual move is to buy a bottle and see what happens. We understand the appeal. But that approach has real costs, and they are not always obvious.
The first is regulation. Under federal law, the FDA does not have the authority to approve dietary supplements before they are marketed, and it generally does not approve supplement claims or labels before use either.[9] The company selling the product is responsible for making sure it is not adulterated or mislabeled.[9] The FDA itself advises talking with a doctor, pharmacist, or other health care professional before using a supplement, in part because some supplements might interact with medicines or other supplements.[9]
The second is that some supplements change your lab results. Biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect results that may go undetected.[10] The FDA has continued to receive reports of biotin causing falsely low results on troponin, a cardiac lab test.[10] If you take biotin, mention it whenever labs are ordered.
The third is that more is not always safer. Too much vitamin D can make the intestines absorb too much calcium, and high blood calcium can lead to kidney stones, kidney damage, confusion, and calcium deposits in soft tissue.[7] Long-term excess zinc can cause copper, iron, or magnesium deficiency.[6] Iron is a special case: a ferritin test can reveal hemochromatosis, a condition where the body already holds too much iron, and MedlinePlus warns that too much iron can cause serious health problems if not treated.[3] MedlinePlus notes that most of the time a provider will measure your iron level before you start supplements.[1]
The fourth is that the cause still matters. MedlinePlus lists tests to look for the cause of blood loss, including a colonoscopy, a fecal occult blood test, and an upper endoscopy, as part of the iron deficiency workup, and it says the outcome with treatment depends on the cause.[1] For B12, it says the anemia will likely get better when the underlying cause is treated.[2] Finding why you are low matters as much as fixing the number.
None of this means supplements are bad. When a test confirms a deficiency, treatment often helps: MedlinePlus notes that iron deficiency anemia often improves or resolves with 6 weeks of iron therapy, with iron continued for another 6 months to replace stores, and that B12 deficiency anemia most often responds well to treatment.[1][2] A ferritin test can also be used to check how well iron treatment is working.[3] So the order matters: test, look for the cause, treat, then recheck. If you already take several products and want a second opinion, our customized supplements service starts with a lab review and a conversation about food, symptoms, and every pill already in your cabinet.
Section 07 / Next steps
When is it not about nutrition, and where do you start in Charleston?
Some signs should go straight to a medical evaluation. Contact a clinician if you notice blood in your stool or stool that looks black and tar-like, since that can mean bleeding that causes iron loss.[1] Heavy menstrual bleeding and pain in the upper belly can also point to the bleeding behind an iron deficiency.[1] When magnesium drops too much it can be a life-threatening emergency, and MedlinePlus lists seizures among the symptoms when levels are extremely low.[4][5] Call 911 for a seizure, new chest pain, fainting, or trouble breathing at rest.
The MedlinePlus pages cited here list causes of these deficiencies that go beyond diet, from bleeding to absorption problems to medicines, which is why the first visit is a medical one, not a shopping trip.[1][2][4] If thyroid symptoms are in the mix, our thyroid management page covers that service, and broader concerns fit under primary care.
If several of these signs fit you, you can book at our Mount Pleasant office or at The Longevity Club in downtown Charleston. Bring your symptoms, a few notes on what you eat, and every medicine and supplement you take. Our annual full panel labs service describes interpreting every result against your symptoms and risk factors, and telling you plainly what is worth acting on and what is simply your normal.
If the bigger issue is how you eat day to day, nutritional therapy is personalized nutrition coaching: a nutritionist on our team builds your meal plan from your lab work, symptoms, and routine, with weekly coaching and goal tracking. For the bigger picture on how a plan like that compares with a short-term diet, see why nutritional therapy works better than diets.
Nutritional Therapy
Personalized nutrition coaching built from your labs and symptoms, with weekly coaching and goal tracking. Read Nutritional Therapy.
Annual Full Panel Labs
A complete blood count, a metabolic panel, and nutrient levels, tailored to your history. Read Annual Full Panel Labs.
Founder, Solcara Health · Diplomate, American Board of Anti-Aging Health Practitioners (ABAAHP)
Ashley has practiced medicine for more than fifteen years. Her path into it began at home, with a family member born with a congenital heart defect and a childhood spent watching how much the quality of a clinician's attention could change the shape of a life. She has since practiced across a range of settings, including medical mission work in Uganda, before founding Solcara to build the kind of practice she kept wishing existed, one that treats patients as whole people and tells them the truth about what the evidence does and does not support.
MedlinePlus (US National Library of Medicine) pages on iron deficiency anemia, vitamin B12 deficiency anemia, magnesium deficiency, zinc, vitamin D, and the ferritin and magnesium blood tests; the US Preventive Services Task Force vitamin D screening recommendation; and FDA pages on dietary supplement regulation and biotin lab interference, each accessed October 5, 2026.
National Library of Medicine. Iron deficiency anemia. MedlinePlus Medical Encyclopedia. 2025. medlineplus.gov
National Library of Medicine. Vitamin B12 deficiency anemia. MedlinePlus Medical Encyclopedia. 2026. medlineplus.gov
National Library of Medicine. Ferritin Blood Test. MedlinePlus Medical Tests. medlineplus.gov
National Library of Medicine. Magnesium deficiency. MedlinePlus Medical Encyclopedia. 2025. medlineplus.gov
National Library of Medicine. Magnesium Blood Test. MedlinePlus Medical Tests. medlineplus.gov
National Library of Medicine. Zinc in diet. MedlinePlus Medical Encyclopedia. 2025. medlineplus.gov
National Library of Medicine. Vitamin D. MedlinePlus Medical Encyclopedia. 2025. medlineplus.gov
US Food and Drug Administration. Questions and Answers on Dietary Supplements. FDA. fda.gov
US Food and Drug Administration. Biotin Interference with Troponin Lab Tests: Assays Subject to Biotin Interference. FDA. fda.gov
Medical Disclaimer: This page is for educational and informational purposes only and does not constitute medical advice, and reading it does not create a patient-provider relationship. It describes general medical information and categories of care, not a recommendation that any individual start, stop, or change any test, treatment, or medication. Any diagnosis or treatment decision requires evaluation by a qualified, licensed clinician who knows your personal and family history. Consult a qualified healthcare provider before making medical decisions. Information reflects sources available as of October 5, 2026.
Ashley Harwyn, PA-C, ABAAHP, is a Diplomate of the American Board of Anti-Aging Health Practitioners (ABAAHP) through A4M and the founder of Solcara Health. Solcara serves South Carolina from Downtown Charleston (163 Rutledge Ave, Ste 202, The Longevity Club) and Mt. Pleasant (496 Bramson Ct, Ste 120).
.webp)
Ashley Harwyn, PA-C
PA-C, ABAAHP · Founder, Solcara Health
Online
