GP Information

Monitoring and blood tests

After discharge from the bariatric surgery service, the patient should have an annual review with their GP.

At their annual review, GPs should check:

• weight
• blood results
• compliance with micronutrient supplements
• maintenance of lifestyle changes

Blood tests

These blood tests are recommended as a minimum and should be done at least annually. If stores are depleted and a patient is on treatment, check more frequently.

Full blood count

• Complete iron profile including serum iron, TIBC, transferrin, ferritin (ferritin level can be normal/high due to acute phase response, normal ferritin level does not exclude depleted iron stores)
• Serum folate (not red cell folate)
• Vitamin B12, holotranscobalamin (active vitamin B12), methyl malonic acid (a functional marker of cellular vitamin B12 deficiency). Holotranscobalamin and MMA are more sensitive and specific markers of vitamin B12 deficiency, as a severely deficient patient can have normal levels of serum vitamin B12. (In absence of availability of active vitamin B12 and MMA, please ensure to maintain the serum vitamin B12 in the upper-normal reference range. You can ask your clinical biochemistry lab to send the sample to the Homerton Hospital lab as a specialist send away test if clinically indicated).
• Bone profile including calcium, phosphate and magnesium.
• Vitamin D and parathyroid hormone (PTH). Elevated PTH suggests secondary hyperparathyroidism due to vitamin D deficiency on a cellular level.
• U&Es
• Liver function tests
• Preoperative diabetes - HbA1c and/or FBG
• Preoperative dyslipidaemia_ - Lipid profiles
• Known thyroid disorders - Thyroid function test

It should not be assumed that abnormal bloods results are always directly related to the surgery itself. There could be potential contributions from physiological and pathological changes in the body, including comorbidities worsened by ageing. High-risk patients might require more frequent monitoring e.g. pregnancy, lactation, acute illness etc.

The BOMSS guidelines for biochemical monitoring and micronutrient replacements can be found here.

Adjustment of regular medications

Improvement in conditions such as type 2 diabetes, hypertension, hyperlipidaemia and obstructive sleep apnoea are often seen following weight loss from bariatric surgery.  People with these conditions should therefore have regular monitoring and adjustments of medications after bariatric surgery.  For people who have type 2 diabetes and no longer require medication, it is still recommended that they have other checks including eye tests and foot health checks on a long term basis, especially if they have had diabetes for a long time as a percentage of patients do relapse.

Patients on thyroxine might require dose reduction following high amounts of weight loss and should be monitored regularly in first year for dose optimisation.

How to refer patients to the Homerton Bariatric Service

The National Institute for Clinical Excellence recommends the use of bariatric surgery as an available treatment option for people with morbid obesity providing they meet all of the following criteria:

• a BMI of 40 kg/m2 or more, or between 35 kg/m2 and 39.9 kg/m2 with a significant health condition that could be improved if they lost weight
• the patient agrees to the necessary long-term follow up after surgery (for example, lifelong annual reviews)
• referral considerations for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background using a lower BMI threshold (reduced by 2.5 kg/m2) than to account for the fact that these groups are prone to central adiposity and their cardiometabolic risk occurs at a lower BMI

To refer a patient to the Homerton Bariatric Service

Referrals have to be made via The Electronic Referral Service (e-RS) using the service’s referral form. Before making a referral, please check the eRS referral form for the inclusion and exclusion criteria. Incomplete referrals will be rejected 

• For patients wishing to be considered for bariatric surgery, please use the service ‘Pre-Operative Bariatric Service - Outpatients 2 – Homerton' on eRS.
• For patients who have had surgery abroad or in the past and experiencing complications, please refer to the BOMSS GP hub for management of complications post-op bariatric surgery.
• For routine post-op referrals please use ‘Post-Operative Bariatric Service - Outpatients 2 – Homerton' on eRS.
• For urgent post op concerns please refer to the BOMSS traffic light poster for primary care management of post operative bariatric patients and refer as appropriate.
• Please contact us if you have any queries through our contact numbers.

Vitamin and mineral supplements are a lifelong requirement after bariatric surgery. Non-compliance with supplementation can result in severe and sometimes irreversible complications. When patients see a healthcare professional, they should support them to continue taking their supplements.

Recommended daily vitamin and mineral supplements

Post gastric band

1.   Over the counter multivitamin and mineral preparation e.g Sanatogen A-Z, Centrum vitamin and mineral once a day. Forceval may be required following NHS prescription in established vitamin and mineral deficiencies as per clinical need.

Post gastric sleeve or bypass surgery

1.   Over the counter multivitamin and mineral preparations e.g. Sanatogen A-Z, Centrum advance twice a day, to be modified based on blood levels of vitamins and minerals. Forceval once a day may be required following NHS prescription in established vitamin and mineral deficiencies as per clinical need.

2.   Maintenance oral dose of vitamin D 3000 IU per day OR 20,000 IU once per week in presence of normal vitamin D level.

3.   Recommend vitamin B12 injections 3 monthly. The frequency of vitamin B12 injections might need to be increased in established severe deficiency. Important note: In patients with both vitamin B12 and folate deficiency, folate supplements should not be given alone, as it can precipitate severe neurological complications (sub-acute combined degeneration of spinal cord). Bariatric patients with B12 level within the normal range should still be given their usual dose 3monthly to prevent levels dropping between reviews.

4. Daily iron supplement – either Ferrous sulphate 200mg daily OR Ferrous fumarate 210mg daily OR Ferrous gluconate 300mg twice daily. ** Iron supplementation needs to be assessed in line with blood test results and additional supplementation may be required. Menstruating women need higher doses: 200mg ferrous sulphate or 210mg ferrous fumarate or 300mg ferrous gluconate tablet twice daily.

The BOMSS guidelines for biochemical monitoring and micronutrient replacements can be found here. 

Nutrients at most risk of malabsorption following bariatric surgery and associated problems:

• Iron
• Vitamin B12
• Folate
• Calcium
• Vitamin D
• Magnesium
• Albumin

Vitamin D, calcium and magnesium

Severe vitamin D deficiency (<30nmol/L) – treat with intramuscular vitamin D injection 300,000 IU followed by oral 20,000 IU colecalciferol two times a week until serum levels returned to normal. Then continue with a usual maintenance regimen of oral 20,000 IU colecalciferol once a week OR 3,000 IU colecalciferol daily. Before starting high doses of vitamin D, hypercalcaemia due to any other cause should be excluded.

Cautions with vitamin D

The total dose of vitamin D should be considered and adjusted accordingly with other medicinal products containing vitamin D. The calcium status and dietary intake of individual patients should also be considered at the same time as starting vitamin D3 replacement or treatment.

Impairment of renal function

Monitor the effect on calcium and phosphate levels.
In severe renal insufficiency, vitamin D in the form of colecalciferol is not metabolised normally and other forms of vitamin D should be used.
Consider risk of soft tissue calcification.

Sarcoidosis or other granulomatous disease

Increased risk of metabolism of vitamin D to its active form.
Monitor calcium in serum and urine.

Primary hyperparathyroidism

Treatment with vitamin D may unmask this.
Monitor serum calcium in susceptible patients.
If calcium levels are raised then it is possible that vitamin D treatment has unmasked primary hyperparathyroidism and a referral should be made to a specialist e.g. endocrinologist if required.

Calcium supplements

Calcium citrate 1000mg per day is a preferred form of oral calcium supplement for patients with past history of calcium-containing kidney stones/other bariatric surgeries. It can be bought from online sources/local health shops as it is not currently available in NHS pharmacies.

Reducing the risk of kidney stones with high-risk patients on calcium supplements

Always take with food.
Drink 2-2.5L water per day.
Diet high in calcium, low in oxalate and low in salt.
During long-term treatment, serum calcium levels and renal function (serum creatinine) should be monitored. Monitoring is especially important in elderly patients on concomitant treatment with cardiac glycosides or diuretics and in patients with an increased tendency to calculus formation. In the case of hypercalciuria (exceeding 300 mg (7.5 mmol)/24 hours) or signs of impaired renal function, the calcium dose should be reduced or the treatment discontinued.

Magnesium

Some patients might need magnesium supplements if they have symptomatic hypocalcaemia. Patients on high doses of vitamin D can have a depletion of tissue magnesium stores and therefore magnesium supplementation is recommended if patient clinically symptomatic or serum magnesium levels are low.

Iron

In cases of depleted iron stores or established iron deficiency anaemia (IDA), oral iron supplements may be required in addition to a patient's usual supplement plan. Some patients might require a higher than the regular therapeutic dose of iron for a short period to treat IDA and replenish iron stores, due to surgery-associated malabsorption, and should be monitored to prevent any iron toxicity. Consider referral to your local hospital for an iron infusion if clinically indicated and oral iron supplements are not sufficient to treat the condition.

Advice for patients on iron supplements

Take with a small amount of orange juice (unless this causes dumping syndrome in the patient). (Vitamin C is known to increase iron absorption but should be used with caution as high doses of vitamin C are known to be associated with increased risk of oxalate-containing kidney stones).
Tea/coffee should be spaced 90minutes away from food and iron supplements.
Patients suffering from severe constipation or bloating on oral iron supplements should be tried on other formulations including liquid formulations (e.g. Feroglobin, Spatone). Sometimes a combination of liquid and tablet formulation might be better tolerated than high daily doses of iron tablets, to reach the appropriate dosage of iron.

Please refer back to the bariatric surgery service at Homerton University Hospital if support and guidance are required regarding complications.

Caption

Complication	Symptoms	Diagnosing	Treatment options
Anastomotic and  stomach ulcers	Upper abdominal pain, vomiting, hematemesis	Upper GI endoscopy in chronic presentation.  (Chest X-ray and CT  abdomen in acute  setting).	1. high dose of proton  pump inhibitors 2. stop smoking 3. eradiation of  helicobacter pylori  infection 4. surgery in acute  presentation (last  option for refractory  ulcers) – refer back  to Homerton
Reflux / Heartburn	Acid reflux, heartburn, coughing at night, reflux on bending	.	Proton pump inhibitors. If problem is persistent, refer back to Homerton.
Strictures / Stenosis	Nausea, vomiting, dysphagia, regurgitation.	Radiological investigations such as barium studies and upper GI endoscopy.	Most strictures can be managed safely with endoscopic dilation.
Internal hernias (gastric bypass)	Cramping, intermittent abdominal pain, nausea with or without vomiting.	Based on clinical suspicion; it can be missed on CT abdomen.	Diagnostic laparoscopy and repair of hernia defects, refer back to Homerton.
Gallstones	Right upper quadrant abdominal pain, some nausea/vomiting	Abdominal ultrasound	Symptomatic gallstones require laparoscopic cholecystectomy, refer to hospital.
Gastric band slippage / erosion	(Slippage) Abdominal pain, vomiting (Erosion) Pain, vomiting, bleeding, intra abdominal abscess, fistula formation, weight regain, loss of restriction	Plain X-ray, barium studies, CT abdomen and upper GI endoscopy	Often removal of gastric band, refer back to Homerton. 1 in 5 patients with gastric band will need revisional surgery at some point following their original operation.

Please refer back to the bariatric surgery service at the Homerton Hospital if support and guidance is required regarding complications.

Caption

Dumping syndrome / Hypoglycaemia	More common after a gastric bypass or duodenal switch procedure.  Symptoms - dizziness, shaking, sweating, palpitations, light headedness, nausea, diarrhoea  Treatment - Dietary modification such as avoiding high sugar and high fat foods and drinks, separating eating and drinking, avoiding long gaps between meals and opting for low glycaemic index (GI) foods. For severe hypoglycaemia a referral back to Homerton University Hospital is recommended.
Kidney stones	Increased risk of kidney stone formation due to enteric hyperoxaluria (increased oxalate absorption) from the gut due to altered gut structure post-surgery (especially gastric bypass and duodenal switch).  Advice - keep water intake to 1.5-2L minimum, low oxalate diet if possible (reduces risk of calcium oxalate kidney stones), calcium supplements should be taken with food (helps binding to oxalate).  In high-risk patients (reduced eGFR, history of kidney stones, single kidney), a 24-urine collection to assess risk of urinary stone formation by measuring stone promoters (calcium, oxalate, sodium) and inhibitors (citrate and magnesium) will be helpful post-surgery.
Osteomalacia and fracture	Prolonged vitamin D deficiency can lead to secondary hyperparathyroidism, which increases loss of bone mass. Patients are then pre-disposed to bone pains, long bone and vertebral fracture. In high risk patients (post-menopausal, on steroids, on thyroxine) regular monitoring of vitamin D and PTH will help in assessing bone metabolism along with DEXA scans, if scans are felt to be indicated.
Wernicke’s encephalopathy (prolonged vomiting)	Patients with prolonged vomiting/diminished food intake can develop severe thiamine deficiency as body thiamine stores lasts for only couple of weeks.  If patient experiences prolonged vomiting always prescribe additional thiamine (thiamine 200–300 mg daily, vitamin B co strong 1 or 2 tablets, three times a day) and urgent referral to bariatric centre. Those patients who are symptomatic or where there is clinical suspicion of acute deficiency should be admitted immediately via A&E for administration of IV thiamine/referred to specialist bariatric unit at HUH.
Neurological complications	Severe neurological deficits can occur due to concomitant multiple nutritional deficiencies e.g. copper, vitamin B12, thiamine. Symptoms - loss of sense of vibration and touch, sub-acute combined degeneration of spinal cord, loss of deep tendon reflexes, severe depression. Urgent referral to specialist bariatric unit recommended.

The BOMSS guidelines for biochemical monitoring and micronutrient replacements can be found here. 

Please refer back to the bariatric surgery service at the Homerton University Hospital if support and guidance is required regarding complications.

table of nutritional complications 

Protein energy malnutrition	It can present at any point after bariatric surgery. Possible causes   – poor dietary protein intake, malabsorption Symptoms   – muscle wasting, weight loss, oedema (although other causes of oedema should also be excluded). Advice   – increase protein intake to >80g/d, if not improve then refer back to Homerton
Severe iron deficiency anaemia	Patients on PPIs are at increased risk. Long-standing deficiency, particularly in females with menorrhagia, can become refractory to oral therapy and require injectable iron preparations.
Severe prolonged  undiagnosed vitamin  B12 deficiency	Patients on PPIs and metformin are at increased risk. It can lead to sub-acute combined degeneration of the spinal cord. Inappropriate folate supplementation in a vitamin B12 deficient patient can aggravate vitamin B12 deficiency related neurological complications – start treating vitamin B12 deficiency before commencing folate treatment.
Severe folic acid  deficiency	Patients on anti-folate drugs, with psoriasis or a condition with high cell turnover (including pregnancy and lactation), are at increased risk. A higher dose may be required due to malabsorptive nature of surgery.
Vitamin A deficiency	Most likely with duodenal switch procedure, or after prolonged diarrhoea and vomiting.  It can lead to problems with vision unless supplemented with high doses of vitamin A.

While bariatric surgery offers significant physical health benefits, it is important for GPs to be aware of potential psychological risks associated with the procedure. Monitoring mental health before and after surgery and maintaining open communication with the patient and their multidisciplinary healthcare team, is essential. Psychological complications may include:

• Emotional Adjustment to Weight Loss
  Significant weight loss can impact patients’ psychological wellbeing. While many expect improved self-esteem and confidence, some may experience distress related to excess skin (Note. Reconstructive surgery is currently not commissioned by the NHS) or body image changes. This can trigger feelings of anxiety, sadness or frustration, potentially leading to mood instability or exacerbation of pre-existing mental health conditions.
• Post-operative Mental Health Changes
  The stress of surgery, recovery and lifestyle adjustments can sometimes precipitate symptoms of depression, mania or psychosis, particularly in patients with complex mental health histories. GPs should closely monitor for any such changes and coordinate care accordingly.
• Disordered Eating and Relationship with Food
  Some patients may develop unhealthy eating behaviours or struggle with their relationship with food post-surgery. This risk is higher in those with prior eating disorders or emotional regulation difficulties. Awareness and early intervention are key.
• Increased Risk of Suicide and Self-Harm
  Research indicates a heightened risk of suicide and self-harm following bariatric surgery, potentially due to altered self-perception, emotional stress or difficulties adjusting. Patients with a history of suicidal ideation or behaviours require careful monitoring and proactive mental health support.
• Alcohol Use and Addiction Transference
  There is evidence that some patients may develop new or increased alcohol use problems after surgery. This may stem from coping challenges or addiction transference, especially in individuals with previous substance use issues. GPs should screen for changes in alcohol use and refer as needed.
• Medication Management
  Weight loss can alter the metabolism of medications, including psychiatric drugs. It is important to review and adjust medications as necessary, in coordination with the prescribing service, and to monitor patients for mood or symptom changes during this period.

If you observe any concerning changes in your patient’s mental health before or after bariatric surgery, please ensure timely notification of the bariatric team and their mental health team, if appropriate.

Bariatric surgery often improves fertility, especially in people with conditions like PCOS or irregular periods. 

It is recommended that women wait 18-24 months after bariatric surgery before considering pregnancy. The oral contraceptive pill is not absorbed the same way after bariatric surgery, so it is recommended that non-oral forms of contraception are used, or two methods of contraception concurrently. 

There are currently no specific guidelines for the management of bariatric patients through their pregnancy; however, the following is a list of recommendations. The RCGP's “Ten top tips for the management of patients post-bariatric surgery in primary care” contains some information regarding pregnancy after bariatric surgery. This can be found on their website.  

Regular nutritional blood screens at a minimum of every trimester increasing to every month if the patient is early post-bariatric surgery (within the first year post-op), has current nutritional deficiencies, is at risk of nutritional issues or has concerning GI symptoms. Continue with regular bariatric post-op blood screens on a 3-4 monthly basis. 

At least two additional growth scans suggested at 26 and 34 weeks gestation alongside the regular 12 and 20-week scans. 

Colecalciferol (vitamin D3) supplementation should be continued, but weekly 20,000IU doses should be swapped for daily (e.g. 3000IU) doses. A pregnancy formulated complete multivitamin and mineral supplement is required twice daily (vitamin A should be in the beta carotene form, such as Forceval or Pregnacare) and vitamin B12 IM 3 monthly injections (if applicable). 

Additional folic acid supplement. Ladies with a BMI of more than 30 are advised to take a higher dose of 5 mg daily for the first trimester. 

It is important for patients to remain off NSAID’s for the prevention of gastric ulcers. If there is no alternative a PPI will need to be taken also. 

It is not appropriate to carry out an oral glucose tolerance test on bariatric patients due to the risk of dumping syndrome. Testing two hours post prandial blood glucose for a week at between 26-28 weeks’ gestation is an option. There are no guidelines in terms of blood results, only suggestions of consistently high readings, looking at HbA1C for long-term exposure of raised blood sugars. A guide would be pre prandial bloods of > 7mmol/l or post-prandial> 11mmol/l, which would then be discussed with the diabetes team. 

It is important that common symptoms experienced during pregnancy are not overlooked such as excessive vomiting and abdominal pain. Rapid weight loss is expected within the first few months after surgery for up to 6 months approximately, however, any sudden or rapid decrease in weight, that is significantly different from the patient’s bariatric weight loss history will need further investigation.  

A referral to an obstetrician with a specialist interest in bariatric surgery should be considered.