If you have had gastric bypass, sleeve gastrectomy or gastric band surgery, regular blood tests are a lifelong clinical requirement — not an optional extra. Bariatric surgery permanently alters how your body absorbs nutrients, and deficiencies can develop silently over months or years without causing obvious symptoms until significant damage has occurred.

The NHS typically discharges bariatric patients from specialist follow-up within one to two years of surgery. Many patients are then left without access to the monitoring their surgery guidelines require. At Tamar Health we offer this service directly, with no GP referral needed, at our Plymouth clinic.

Why blood tests are essential after bariatric surgery

Bariatric surgery works by restricting food intake, reducing nutrient absorption, or both. Gastric bypass and sleeve gastrectomy significantly reduce the surface area available for absorption and alter gut hormone signalling. Even with good dietary habits and supplementation, certain nutrients cannot be absorbed adequately without regular monitoring to catch shortfalls early.

The most common deficiencies seen after bariatric surgery include:

• Iron and ferritin — reduced stomach acid and bypassed duodenum impair absorption. Iron deficiency anaemia is the most common long-term nutritional complication.
• Vitamin B12 — requires intrinsic factor produced in the stomach. Reduced stomach volume means reduced production; deficiency causes nerve damage and anaemia.
• Vitamin D and calcium — bypassed duodenum is the primary site of calcium absorption. Undetected deficiency leads to metabolic bone disease and osteoporosis.
• Folate — reduced food intake and altered absorption. Important for red cell production and neurological function.
• Zinc, magnesium and thiamine — commonly depleted, particularly in the first year. Thiamine deficiency (B1) can cause irreversible neurological damage if untreated.
• Copper and selenium — less commonly monitored but included in 12-month and annual checks per BOMSS guidance. Deficiency is rare but serious.

Gastric Bypass & Sleeve Gastrectomy Monitoring

These procedures carry the highest malabsorption risk. BOMSS guidelines recommend testing at 3 months, 6 months and 12 months post-operatively, then annually for life. The panel expands at each stage as the risk profile changes.

3 months post-operative

First post-operative check. Establishes a baseline, identifies early deficiencies from reduced intake during the immediate recovery period, and checks metabolic markers before they become established problems.

6 months post-operative

Extended panel. Bone markers are added at this stage as PTH begins to rise in response to calcium and vitamin D insufficiency, often before vitamin D levels themselves appear critically low.

12 months post-operative

Full first-year panel. Copper and selenium are added for the first time — deficiency becomes more relevant after a full year of altered absorption.

Annual monitoring (ongoing, for life)

The 12-month panel continues annually for life. This is the minimum recommended by BOMSS for bypass and sleeve patients regardless of how many years have passed since surgery.

Adjustable Gastric Band Monitoring

Gastric bands are restrictive only — they do not bypass any part of the digestive tract. Malabsorption risk is lower than with bypass or sleeve surgery, but deficiencies can still develop due to reduced food intake, particularly of iron, B12 and vitamin D. BOMSS guidelines recommend monitoring at 6 months post-operatively, then annually.

6 months post-operative

Annual monitoring (ongoing)

Pricing

Post-bariatric panels are not a fixed profile — the tests required change depending on your surgery type, how long ago you had it, and what has been checked recently. We confirm the exact panel at booking and price accordingly. All prices are all-inclusive patient totals with phlebotomy included.

How it works

• Book your appointment — call us or book online. Let us know your surgery type and when it was performed and we will confirm the correct panel before you arrive.
• Attend your blood draw — a qualified phlebotomist takes your samples at our Plymouth clinic. Most bariatric panels require two to three tubes. Appointments take around 15–20 minutes.
• Receive your results — samples are sent via pre-paid tracked courier to our laboratory. Most results are returned the next working day.
• Clinical review available — if any results fall outside normal range or you would like a clinician to review your results and advise on supplementation, a follow-up telephone or face-to-face appointment is available.

Common questions

See all blood tests

Our full blood test price list covers over 40 profiles including general health screens, hormone panels, thyroid, digestive health and more. View the full blood test price list.