If You’re Having Fertility Troubles, Have You Looked at Your B12 Intake?


I used to think that taking a Centrum multivitamin would take care of all my body’s nutritional needs. Now I know better. Most over the counter supplements are not monitored for quality or content by an independent lab and frequently do not contain the ingredients advertised. At any rate, I would much rather get my vitamins from my produce section and farmer’s market than from a bottle, but as a woman with Polycystic Ovarian Syndrome (PCOS), sometimes food sources just are not enough.

There are certain vitamins that are commonly lacking from our diets and require supplements. Vitamin D, for example, gets a lot of press. You may not know about another common deficiency: critical “B” vitamin B12. People become depleted of B12 for many reasons with serious consequences, such as fertility issues, fatigue, lethargy, weakness, memory loss, neurological and psychiatric problems and anemia. Frighteningly, many common diseases (such as Alzheimer’s, cardiovascular disease, mental illness, autoimmune diseases and more) have symptoms that mimic those of B12 depletion and are easily misdiagnosed.

What Is B12?

One of the eight B vitamins, B12 is a water-soluble vitamin that helps your brain and nervous system function. It’s actually the largest vitamin and plays a big role in your body’s cells metabolizing.

Who Is Low In B12?

Data from the Tufts University Framingham Offspring Study suggests that 40 percent of people between the ages of 26 and 83 have plasma B12 levels in the low normal range — a range at which many experience neurological symptoms. Nine percent had deficiency, and 16 percent exhibited “near deficiency.” Most surprising to the researchers was that low B12 levels were common in younger people.

Where Do You Get B12?

Vegetarians and vegans take note! B12 is only found in animal based food. Here are some of the top B12 containing foods:  

  • Mollusks (clams, oysters, mussels)
  • Beef liver
  • Salmon
  • Wild trout
  • Sirloin Beef

Vegetarians and vegans should understand that there are no plant sources of B12, and studies consistently show that up to 50 percent of long-term vegetarians and 80 percent of vegans are deficient in B12.

What Are the Symptoms of B12 Deficiency?

  • Premature gray hair
  • Disturbed carbohydrate metabolism
  • Fatigue
  • Weakness
  • Dizziness
  • Weight loss
  • Constipation
  • Infertility
  • Vision problems
  • Loss of hearing and tinnitus
  • Numbness and tingling in the hands and feet
  • Alcoholism
  • Incontinence
  • Hyperpigmentation and hypopigmentation (dark and light patches in the skin)
  • Psoriasis and other skin problems
  • Insomnia
  • Irrational or chronic anger
  • Violent behavior
  • Lack of balance/abnormal gait
  • Any emotional disorder

A Note About B12 and Infertility

“Vitamin B12 deficiency is associated with infertility,” says hematologist Michael Bennett, M.D., in Could It Be B12? “Pregnancy may occur in the presence of B12 deficiency but may be associated with recurrent early fetal loss.” Luckily, supplementation can help. Doctors have reported successful pregnancies in once-infertile women following therapy for B12 deficiency. If you are going through fertility treatments, insist on a B12 test.

What Causes B12 Deficiency?

There are many causes, ranging from poor diet, to medication side effects to other medical conditions (such as leaky gut and/or gut inflammation, low stomach acid, pernicious anemia, alcohol use, and exposure to nitrous oxide).


  • Metformin causes B12 deficiency.
    I know when I was taking metformin, my doctor never told me that I could become B12 deficient and was never told to supplement. If you are taking metformin for type 2 diabetes, talk to your doctor about supplementing with B12 and have your levels checked regularly.


  • Oral contraceptives may cause B12 deficiency.
    The data regarding the effects of oral contraceptives on vitamin B12 serum levels are conflicting. Some studies have found reduced levels in oral contraceptive users, but others have found no effect despite use of oral contraceptives for up to 6 months. When oral contraceptive use is stopped, normalization of vitamin B12 levels usually occurs.

What Tests Can I Take to Know If I Am Low In B12?

  • B12: Normal values are 200 – 900 pg/mL (picograms per milliliter)
  • CBC (Complete Blood Count): This is actually a group of tests ordered routinely to screen for blood cell abnormalities. It measures cell types, quantities and characteristics. With both B12 and folate deficiencies, the amount of hemoglobin and RBC count may be low, and the RBCs are abnormally large (macrocytic or megaloblastic), resulting in an anemia. White blood cells and platelets also may be decreased.
  • Methylmalonic Acid (MMA): This is sometimes ordered to help detect mild or early B12 deficiency. A normal serum sMMA level is .07 to .27 µmol/l. A normal urine uMMA level is .58 – 3.56 µmol/mmol.
  • Homocysteine (HCY): This one is only occasionally ordered. Levels may be elevated in both B12 and folate deficiency. A normal serum HCY is 2.2 – 13.2 µmol/l.

If MMA and homocysteine levels are increased and the vitamin B12 level is mildly decreased, an early or mild B12 deficiency may be present. This may indicate a decrease in available B12 at the tissue level. If only the homocysteine level is elevated, then the person may have a folate deficiency. If both MMA and homocysteine levels are normal, then it is unlikely that there is a B12 deficiency.

Supplementing B12

The most commonly used form of supplemental B12 in the US is cyanocobalamin — that is what you will find in your basic Centrum vitamins. However, only two forms of B12 are active in the body — methylcobalamin and adenosylcobalamin. Cyanocobalamin must be converted in the body to either methyl or adenosyl cobalamin. If you supplement with methylcobalamin, your body can immediately use this active form of vitamin B12. This type, which is available at most health food stores, can be supplemented in pill form, sublingual tablet, liquid, transdermal patch, nasal spray, and even lollipop. If your B12 is really low, your doctor may prescribe injections. The standard protocol is 1,000 micrograms daily for three days, then weekly for a month, then one injection per month indefinitely.

Be sure that you chose a B12 supplement that is verified by a third party, independent lab. Otherwise, you cannot be certain that the quality or quantity you are consuming is accurate. In some cases, uninspected supplements contain none of the nutrients advertised! For guidelines on how to choose a quality supplement, read, Choosing the Right Supplement for PCOS: Not All Supplements Are Created Equal.

Speak Up!

Ask to have your B12 tested. Most physicians do not routinely test B12. Even if you are within “normal” ranges you could be too low for you. People with B12 levels between 200 pg/mL and 350 pg/mL are considered “low-normal” in the U.S. In Japan and Europe, the lower limit for B12 is between 500-550 pg/mL.

Want to learn more about PCOS from Amy? Find more on her Expert Spotlight

Want more? You Might Also Like:

10 Superfoods for a Happy, Healthy Gut

Gone Gluten-Free? A Dietitian Reveals 9 Essential Nutrients You May Be Missing

What’s the Difference Between Celiac Disease, Gluten Intolerance, and Wheat Allergies? A Registered Dietitian Explains


Note: PLEASE consult with  your doctor before making any changes to your diet or medications. The material on this site is provided for educational purposes only, and is not to be used for medical advice, diagnosis or treatment.

PCOS Diva.com is an online resource for women with PCOS which embraces a holistic approach to healing and thriving. As the founder of PCOS Diva, Amy Medling, CHC has worked with thousands of women, teaching them how to make sustainable lifestyle changes, which in turn positively impacts their health and lessens PCOS symptoms. “PCOS Divas” are able to take back control of their bodies and regain their fertility, femininity, health and happiness. Check out her Seasonal Meal Plans, PCOS 101 guide and 7-day lifestyle coaching Jumpstart program. For more about PCOS Diva, Amy’s philosophy and PCOS Diva’s programs, check out the About section of the website.



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