Should you see a doctor before buying a supplement?

When a supplement is a reasonable choice on its own

Some supplements are recommended for whole groups of people in the UK. Everyone is advised to consider 10 micrograms of vitamin D a day, at least in autumn and winter, because between late March or April and the end of September most people aged 5 and over make enough from sunlight [1]. People who are rarely outdoors or who usually cover most of their skin are advised to take it all year, and people with dark skin should consider doing the same [1].

Women who could become pregnant are advised to take 400 micrograms of folic acid a day until the 12th week of pregnancy, and women with diabetes or who take antiepileptic medicines should ask a doctor, because they may need a higher dose [1].

What a supplement can and cannot do

In the UK, a food supplement is regulated as food. It is not a medicine and is not intended to treat or prevent disease [2]. Most products contain amounts below the safe upper levels set by UK experts, though a small number contain enough to cause side effects in some people [3].

For prevention in healthy adults, the evidence is limited. The US Preventive Services Task Force found the evidence insufficient to judge whether multivitamins or most single nutrients prevent heart disease or cancer, and it recommends against beta carotene and vitamin E for that purpose [4].

A supplement label in Great Britain may carry only the health claims on the authorised register. For vitamin D these include that it contributes to the maintenance of normal bones and to the normal function of the immune system [5]. Wording that promises to cure, prevent or treat a condition is a sign the product is being sold outside the rules.

Natural does not always mean safe. Herbal products and weight loss products described as natural can still interact with medicines or be unsuitable for people with certain conditions [6].

When to see a doctor first

A short consultation before you buy is worth it if any of these apply to you.

• You have a symptom you hope a supplement will fix, such as tiredness, low mood, poor sleep or hair loss, which may have a cause that needs a diagnosis.
• You take prescription medicines, particularly for the heart, depression, HIV or contraception, or a blood thinner such as warfarin [6].
• You are pregnant, breastfeeding or buying for a child [6].
• You have a long-term condition, a recent illness or planned surgery [6].
• You are considering a high dose, or several products that contain the same nutrient [3].

Symptoms a supplement should not cover

Some symptoms need a doctor before anything else. NICE lists unexplained weight loss as a symptom of several cancers, and names unexplained weight loss, fatigue or a change in bowel habit as reasons for women to have tests [7]. Tiredness that does not lift, weight loss you cannot explain, a change in bowel habit, unexpected bleeding or a new lump all deserve a consultation first.

If you have chest pain, sudden breathlessness, signs of a stroke or a severe allergic reaction, call 999 in the UK or the local emergency number.

A checklist before you buy

These questions help whether you decide alone or with a doctor.

• What exactly do I want this to do, and is there evidence for it in someone like me?
• Would a blood test show whether I am actually low in this nutrient?
• Could it interact with any medicine I take [6]?
• Will I stay within the daily dose on the label, without doubling up across products [2]?
• For a herbal medicine, does the pack show a Traditional Herbal Registration mark or a product licence number, which shows it is licensed by the MHRA [8]?

Who each route suits

Buying on your own suits a healthy adult following UK advice, such as vitamin D through the winter, or someone continuing a supplement a doctor has already agreed. A consultation first suits anyone with symptoms, regular medicines, pregnancy or a long-term condition, and anyone who would like to know whether they need a supplement at all.

The two routes work well together. Many people check once with a doctor, settle on what suits them, and then buy and review it with confidence, returning when their health, medicines or plans change.

How The Wellness can help

A telephone consultation with a GP the same day gives you a clear answer before you spend anything. If a test would settle the question, the Core Wellness blood test includes iron stores, thyroid function and vitamin D, and a doctor explains the results with you.

When you know what you need, The Wellness shop stocks supplements you can choose with that advice in hand. Every doctor is GMC registered, our clinics are on Baker Street in Marylebone and Eccleston Street in Belgravia, and a doctor can come to your home or hotel in London.