Post-bariatric surgery nutrition check

For follow-up

Nutrition blood test after bariatric surgery, such as gastric bypass or gastric sleeve (sleeve gastrectomy), with vitamin B12, folic acid, iron, vitamin D, PTH, vitamin A, copper, zinc, selenium, magnesium, proteins and general biochemistry. It is designed for periodic monitoring of deficiencies that can appear differently depending on the technique and the time since surgery.

No prescription or appointment needed

Results in 5-7 working days

Blood and urine sample. Includes: Full blood count · Glucose · Urea, creatinine and eGFR · Uric acid · Sodium and potassium · Lipid profile and ratios. 23 in total. See what each one measures

What it is for

It reviews deficiencies of iron, B12, folate, vitamin D, vitamin A, zinc and copper after bariatric surgery. It also assesses PTH, proteins and general parameters that help identify problems with intake, absorption or supplementation.

It is designed to be repeated as part of the follow-up by the team that monitors the surgery. The frequency is not the same for everyone: it is usually higher during the first year and is then adapted to the technique, previous results, symptoms and supplementation.

When it is recommended

Periodic follow-up after a gastric bypass or a sleeve gastrectomy
First-year checks together with the surgical or nutrition team
Reviewing an established supplementation regimen
Anaemia, hair loss, weakness or nutritional abnormalities after surgery
Neurological or visual symptoms require prompt medical assessment and may call for additional tests

Clinical comment

Copper is included because its absorption can fall after a bypass and because high doses of zinc reduce its availability even further. A deficiency can cause anaemia, neutropenia and neurological symptoms that resemble those of B12 deficiency. Caeruloplasmin helps interpret the result, although it also changes with inflammation and other situations.

PTH can rise before blood calcium falls, in response to insufficient intake or absorption of calcium and vitamin D. However, PTH should not be interpreted on its own. This profile does not include calcium in its current composition, so calcium has to be added, or a recent result has to be available, if PTH is raised.

Vitamin A makes more sense in this context because of the risk of malabsorption. Even so, this protocol does not cover every nutritional emergency. Persistent vomiting, rapidly worsening weakness, confusion, difficulty walking or visual disturbances require medical assessment without waiting for a routine check, especially because of the risk of thiamine deficiency or other complications.

Dr. Antonio Mas

What is tested

Full blood count: Looks for anaemia and other changes in the blood cells.
Glucose: Allows the metabolic course after surgery to be compared.
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, although it can also rise with inflammation.
Iron studies (iron, transferrin, saturation and total iron-binding capacity)
Vitamin D (25-OH): Assesses vitamin D stores.
Vitamin A (retinol): Helps identify a deficiency with techniques or situations that involve fat malabsorption.
Vitamin B12: Assesses a vitamin whose absorption can fall after surgery.
Folic acid (folate): Completes the assessment of anaemia and micronutrients.
Magnesium: Measures serum magnesium.
Zinc: Assesses a mineral that can fall because of lower intake or absorption.
Selenium: Completes the assessment of trace elements in cases of nutritional risk.
Copper: Can show a deficiency that may cause anaemia and neurological symptoms.
Caeruloplasmin: The main copper-carrying protein, which helps interpret the copper level.
Intact PTH: Can rise in response to insufficient intake or absorption of calcium and vitamin D.
Homocysteine: Adds functional context about B12 and folate, although it is not specific.
Total protein and albumin: Help assess synthesis, losses and nutritional risk.
Urinalysis and sediment: Looks for protein, blood, glucose, white blood cells and other urinary abnormalities.
TSH: The first test of thyroid function.

How to prepare

Fast for 8 to 12 hours. You can drink water. Bring a sample of your first urine of the morning or collect it at the partner centre. If you take biotin supplements, stop them 48 hours before, because they can interfere with several tests.

Do not stop your prescribed bariatric supplements. Oral iron can temporarily change serum iron; check whether you should have the sample taken before your dose. Bring a note of the supplements and the amounts 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

Related blood tests

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

The most comprehensive is not always the most useful. If you are not sure, the one we recommend to start with is Basic nutrition blood test.

What it is based on

American Society for Metabolic and Bariatric Surgery · Surg Obes Relat Dis 13(5):727-741
ASMBS Integrated Health Nutritional Guidelines for the Surgical Weight Loss Patient 2016 Update: Micronutrients
This is the guideline this profile is built on, and the one that sets how often it is done: it defines routine monitoring as every three to six months in the first year and yearly after that. It calls for yearly screening of copper and zinc after a bypass even without any symptoms, and vitamin A within the first year, and it explains why copper goes with zinc: the high doses of zinc prescribed after surgery can cause copper deficiency. For vitamin D it proposes reading it in combination with PTH, which is what is included here, and it warns that ferritin alone is not enough to assess iron, which is why it comes with full iron studies. One point where this profile falls short: the guideline asks for copper and caeruloplasmin to be measured together.

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.