Complejo B: Ingredients, Uses, Dosage, Side Effects, Benefits

Complejo B is the Spanish word for supplements that contain B Complex vitamins which usually deliver eight of the B vitamins: B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin). Complejo B is used to treat or prevent vitamin deficiency due to poor diet, certain illnesses, alcoholism, or during pregnancy. Vitamins are important building blocks of the body and help keep you in good health.

Each component of Complejo B has a unique structure and performs unique functions in the human body:

  • Vitamin B1 – thiamin. Vitamin B1 is vital to the healthy growth and function of organs, including the brain and heart.
  • Vitamin B2 – riboflavin. The body needs vitamin B2 to break down fats and drugs.
  • Vitamin B3 – niacin. The body needs niacin to maintain healthy skin, nerves, and digestion. Doctors sometimes prescribe high doses of niacin to help improve cholesterol levels.
  • Vitamin B5 – pantothenic acid. Vitamin B5 is essential for the health of the brain and nervous system.
  • Vitamin B6 – pyridoxine. Vitamin B6 helps the body make new red blood cells, which carry oxygen throughout the body. It also helps keep the immune system strong.
  • Vitamin B7 – biotin. Biotin is essential for healthy hair, nails, and nerve function.
  • Vitamin B9 – folic acid. The body uses folic acid — or folate, its natural form — to make DNA and genetic material. Before and during pregnancy, sufficient amounts of folic acid help to reduce the risk of certain birth defects.
  • Vitamin B12 – cobalamin. The body’s nerves and blood cells require vitamin B12. Adequate levels of B12 also prevent pernicious anemia, which is a deficiency of this nutrient.

Megadoses of Complejo B sometimes taken to combat everyday stress, boost energy, or control food cravings, do not appear to offer benefit unless a person is deficient in one or more of them.

Is Neurobion the same as Complejo B?

Yes, Neurobion is similar to Complejo B tablets. It is a multivitamin that contains a mixture of six B vitamins, mainly Vitamin B3, B6, and B12. Neurobion is prescribed to people who might suffer from deficiency of different Vitamin B derivatives and develop signs of anemia, fatigue, and tiredness.

Does Complejo B help you lose weight?

Yes. Vitamin B12 in Complejo B is popular for weight loss. Intake of Vitamin B12 helps to fight fatigue, boost energy levels, and speed up body metabolism. However, Complejo B is a multivitamin supplement that should not be used for weight loss. We recommend that you consult a doctor for such a case.

How to take Complejo B

Take Complejo B orally and once a day. Take this drug with a full glass of water (8 ounces or 240 millilitres). Chew the tablet carefully before swallowing if you’re taking chewable tablets.

The recommended dose of Complejo B Capsule is 1 capsule taken by mouth, usually once daily or as directed. Swallow them whole if you’re taking extended-release capsules. Follow all directions on the product package. If you have any questions, ask your doctor or pharmacist. Many doctors recommend 100 mg of Complejo B vitamins per day. Double-blind research suggests that supplementing with Complejo B multivitamins may reduce feelings of anxiety, perceived stress, and tiredness.

The daily recommended dosage of Complejo B can also vary for different people.

•          For young adults, 400 micrograms (mcg) daily.

•          Lactating mothers require 500 mcg a day.

•          600 mcg a day for pregnant women and older adults.

Some people are at an increased risk of deficiency—particularly those who are over the age of 50, take antacid medication, or have celiac disease, Crohn’s disease, gastritis, or other digestive disorders. If you have had stomach or weight loss surgery, drink alcohol regularly, or follow a vegetarian or vegan diet, you may also be more prone to a deficiency. People who are pregnant or breastfeeding may need more vitamins B6, B12, and folate.

Complejo B  side effects

Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Belly pain
  • Change in color of stool to green
  • Constipation
  • Diarrhea
  • Upset stomach or throwing up

Serious side effects

Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking B Complejo. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.


Complejo B does not interfere adversely with other drugs in most cases. However, such medications may increase the risk of vitamin B deficiency. Examples of drugs that can result in low levels of particular B vitamins are as follows:

  • Drugs for blood pressure and chemotherapy drugs will reduce the B-1 levels of an individual.
  • B-3, B-6, and B-9 levels may be reduced by antiseizure drugs used for epilepsy
  • Low levels of B-3 and B-6 can be caused by drugs that treat tuberculosis

Can Vitamin C and Complejo B be taken together?

In small doses, Vitamin C and Complejo B do not interact with one another. However, in large quantities, Vitamin C is known to interfere with Vitamin B12 absorption and metabolism. Additionally, large doses of Vitamin C may interact with supplements that could have a hormonal, antibacterial, and blood-thinning impact.


Dr. Oche Otorkpa PG Cert, MPH, PhD

Dr. Oche is a seasoned Public Health specialist who holds a post graduate certificate in Pharmacology and Therapeutics, an MPH, and a PhD both from Texila American University. He is a member of the International Society of Substance Use Professionals and a Fellow of the Royal Society for Public Health in the UK. He authored two books: "The Unseen Terrorist," published by AuthorHouse UK, and "The Night Before I Killed Addiction."
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