Basic nutrition blood test

First line

Basic vitamin and mineral blood test with vitamin D, vitamin B12, folic acid and ferritin, plus full blood count, glucose, cholesterol, kidney and liver function, electrolytes and TSH. It is a first nutritional assessment for tiredness, hair loss or a limited diet, with parameters that help tell deficiencies apart from other common causes.

No prescription or appointment needed

Results in 1-2 working days

Includes: Full blood count · Glucose · Urea, creatinine and eGFR · Uric acid · Sodium and potassium · Lipid profile and ratios. 12 in total. See what each one measures

What it is for

It serves as a first review of nutritional status and the general picture. It shows whether there are low iron stores, abnormal vitamin D, B12 or folate, and changes in the full blood count, thyroid, kidneys or liver that may help explain the symptoms.

Bear in mind that tiredness and hair loss are very non-specific symptoms. A normal blood test cannot exclude all their causes, and a slightly low vitamin does not necessarily prove that it is responsible.

When it is recommended

Persistent tiredness whose cause has not been investigated
Hair loss or brittle nails together with suspected iron or other nutrient deficiency
A restrictive or limited diet kept up over time
A history of low vitamin D, B12, folate or ferritin
Before starting several supplements without knowing the starting point

Clinical comment

We have included TSH because hypothyroidism can cause tiredness, weight changes, dry skin, constipation or hair loss, symptoms that are easily blamed on a nutritional deficiency. This does not mean that everyone with tiredness should have an extensive thyroid assessment: TSH is the first step, and an abnormality is then confirmed with free T4.

Ferritin also requires context. A low value supports iron deficiency, but a normal or high value does not always exclude it if there is inflammation. This profile gives a first measure of stores; if the result does not fit, the full nutrition blood test adds iron, transferrin and transferrin saturation.

We have not added a long list of micronutrients because measuring more does not always make things clearer. This profile prioritises common deficiencies and general biochemistry; trace minerals are kept for diets, symptoms or histories that make them relevant.

Dr. Antonio Mas

What is tested

Full blood count: Looks for anaemia and other changes in the blood cells.
Glucose: Measures fasting blood sugar.
Urea, creatinine and eGFR: Assess kidney function and add context about hydration and protein metabolism.
Uric acid: Completes the metabolic and kidney assessment.
Sodium and potassium: Measure the main electrolytes in the blood.
Lipid profile (total cholesterol, HDL, LDL, triglycerides) and ratios
AST, ALT, GGT and total bilirubin: Give information about the liver.
Ferritin: Estimates iron stores and can show iron deficiency before anaemia appears, although it also rises with inflammation.
Vitamin D (25-OH): The measurement used to assess vitamin D stores.
Vitamin B12: Can show a low or indeterminate level of cobalamin.
Folic acid (folate): Assesses folate, which is involved in making blood cells.
TSH: The first test for identifying a thyroid disorder that could cause similar symptoms.

How to prepare

Fast for 8 to 12 hours. You can drink water. If you take biotin supplements, which are common in hair and nail products, stop them 48 hours before, because they can interfere with TSH and other tests. Do not stop other prescribed supplements without checking first, and say which ones you take.

You can add

Without another needle. It is offered when you order, so you do not have to decide now.

Sugar, insulin and inflammationAssesses insulin resistance through fasting insulin and the HOMA-IR index, plus average blood sugar over the last three months and low-grade inflammation.+€59.00
Coeliac disease antibodiesMeasures the antibodies used to investigate coeliac disease; for a reliable result, it must be done while you are still eating gluten.+€39.00

Related blood tests

We have other profiles in Nutrition with more or fewer tests:

The most comprehensive is not always the most useful. This is the one we recommend to start with; the others cover specific situations.

What it is based on

Organización Mundial de la Salud
WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations
This is the guideline that supports assessing iron through ferritin, which is what this profile does. It also carries a warning worth knowing: ferritin rises with inflammation, so the WHO asks for it to be read alongside acute-phase markers such as CRP and raises the threshold to 70 µg/L when infection or inflammation is present. In that scenario ferritin alone falls short, and the full iron studies in the full nutrition blood test say more.
National Institute for Health and Care Excellence
Vitamin B12 deficiency in over 16s: diagnosis and management (NG239)
It places blood B12 as the first test and defines who it is requested for: people with at least one symptom and at least one risk factor, and a diet low in animal products is one of the factors on that list. The rest of the panel (vitamin D, folic acid and TSH) does not come from a guideline that covers it as a whole. It is the combination usually requested at a medical appointment for tiredness lasting months, and that is how it should be read: usual clinical practice, not a published recommendation.

Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.

This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.