It depends on the person condition.

Is there a deficiency of vitamin B comlex or not?.

Did the doctor give it to the patient as a supplement to increase appetite or as an adjunct with another treatment causing vitamin deficiency.

Each case has its own status and appropriate therapeutic dose.

B vitamins and Health:

Article B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review

Article Vitamin B-12 in Health and Disease

Article Vitamin B Supplementation: What's the Right Choice for Your Patients?

Article B vitamins and berries and age-related neurodegenerative disorders

Dietary Reference Values:

https://www.efsa.europa.eu/sites/default/files/2017_09_DRVs_summary_report.pdf

What are the benefits?

B vitamins play a vital role in maintaining good health and well-being. As the building blocks of a healthy body, B vitamins have a direct impact on your energy levels, brain function, and cell metabolism.

Vitamin B complex helps prevent infections and helps support or promote:

- cell health

- growth of red blood cells

- energy levels

- good eyesight

- healthy brain function

- good digestion

- healthy appetite

- proper nerve function

- hormones and cholesterol production

- cardiovascular health

- muscle tone

Vitamin B complex play a vital role in maintaining good health and well-being. As the building blocks of a healthy body, they have a direct impact on energy levels, brain function, and cell metabolism. Vitamins B1, B3, B6, B9 and B12 are essential for neuronal function and deficiencies have been linked to depression. However, intake of high levels of vitamin B6 from supplements for a year or longer may cause severe nerve damage. Other signs of too much vitamin B6 include painful, unsightly skin patches, extreme sensitivity to sunlight and nausea.

Please have a look at this useful link.

https://www.pharmatutor.org/pdf_download/pdf/Vol.%203,%20Issue%2011,%20November%202015,%20PharmaTutor,%20Paper-7.pdf

It depends on the person condition.

Is there a deficiency of vitamin B comlex or not?.

Did the doctor give it to the patient as a supplement to increase appetite or as an adjunct with another treatment causing vitamin deficiency.

Each case has its own status and appropriate therapeutic dose.

Recommended Dietary Allowances

The recommended dietary allowances, which are established by the Institute of Medicine, are based on gender and age and should only be used as a guideline. Certain medical conditions or lifestyles may influence the recommended amount of vitamins you should get. Generally speaking, most healthy adult men and women should consume approximately 2.4 mcg of vitamin B-12, 1.3 mg of vitamin B-6, 400 mcg of folate, 5 mg of pantothenic acid and 30 mcg of biotin. Men need 16 mg of niacin, 1.2 mg of thiamin and 1.3 mg of riboflavin, while women should have 14 mg of niacin, 1.1 mg of thiamin and 1.1 mg of riboflavin. Pregnant and nursing women should check with their doctor since they will require more of each nutrient

The many articles have shown that taking a B-complex as a supplement may be helpful even for men and women who don't have an increased need for these nutrients. However, taking supplements that contain excessively high and unnecessary quantities of B-complex vitamins could lead to serious side effects.

High doses of B3 may lead to vomiting, high blood sugar levels, skin flushing, and even liver damage. Moreover, high doses of B6 can cause nerve damage, light sensitivity, and painful skin lesions. Last side effect is that it can turn urine bright yellow. Also, I think it is one of the causes of gout attacks.

Thanks Dr. Arvind Singh sir and Dr. Nihada Ahmetovic mam for sharing the important article links.

Although Vitamin B complex are known for their benefits but dosage & Suitability of these supplements depend upon person to person. These never suits me.

Vitamin B complex play a vital role in maintaining good health and well-being. As the building blocks of a healthy body, they have a direct impact on energy levels, brain function, and cell metabolism. Vitamins B1, B3, B6, B9 and B12 are essential for neuronal function and deficiencies have been linked to depression. However, intake of high levels of vitamin B6 from supplements for a year or longer may cause severe nerve damage. Other signs of too much vitamin B6 include painful, unsightly skin patches, extreme sensitivity to sunlight and nausea. Agree with friend

The dose is determined individually, depending on the type and severity of the deficiency. In anemia (deficiency due to impaired vitamin absorption) in adults, a dose of 1,000 micrograms is administered twice in the first week, and 100-200 micrograms per month, by injection, until anemia disappears. A larger dose, up to 1,000 micrograms of B12, can be given, along with folic acid, in severe deficiencies.

The dose is determined individually, depending on the type and severity of the deficiency. In anemia (deficiency due to impaired vitamin absorption) in adults, a dose of 1,000 micrograms is administered twice in the first week, and 100-200 micrograms per month, by injection, until anemia disappears. A larger dose, up to 1,000 micrograms of B12, can be given, along with folic acid, in severe deficiencies.

Why not, the information is developed every day. The question, reminding, and intellectual overlap of a given task may open doors unexpected about a common topic