Antiseizure medication...impact on weight and health - Specialist Nutrition Rehab


18 Jan 2023

Antiseizure medication…impact on weight and health

Antiseizure medication (sometimes also called antiepileptic or anticonvulsant medication) is commonly prescribed to people after a traumatic injury.  This medication is sometimes used to manage seizures/ epilepsy, but can also be prescribed for other conditions, such as neuropathic pain and/or mood disorders. Commonly prescribed varieties include carbamazepine, lamotrigine, levetiracetam, sodium valproate, pregabalin and gabapentin.

Antiseizure medication plays a vitally important role in the management of certain symptoms.  However, it’s important for health professionals, case managers and solicitors to be aware of the impact that this medication can have on weight and other health parameters.  Clients will need to be monitored appropriately to ensure that the medication does not negatively impact their health.


Common side effects

Side effects will be influenced by the dosage and duration of use.  Sometimes multiple antiseizure medications are used simultaneously, in which case side effects may increase.

Clients should never stop taking their antiseizure medication without the advice of their neurologist, GP or other consultant.  Any unwanted side effects should be discussed with them.

1.  Weight changes and cardiovascular risk (1, 2, 3, 4, 5)

Weight gain is one of the most common side effects of antiseizure medication and will usually start within the first three months of treatment.  Typically, 58-70% of adults will gain weight, 10-11% will maintain their weight and 30% will lose weight, depending on which medication is used.

  • Risk of weight gain – carbamazepine, gabapentin, oxcarbazepine, perampanel, pregabalin, valproate and vigabatrin.
  • Weight neutral – eslicarbazepine, lacosamide, lamotrigine, levetiracetam, phenytoin, tiagabine.
  • Risk of weight loss – cannabidiol, felbamate, rufinamide, stiripentol, topiramate, zonisamide.

Weight gain has been attributed to high insulin levels, increased appetite, altered metabolism of fat and glucose, as well as other mechanisms which are not yet well understood.  Fortunately, regular physical activity has been found to help prevent weight gain from antiseizure medication.

Any weight that is gained, will increase a person’s risk of type 2 diabetes, cardiovascular disease and non-alcoholic fatty liver disease.  Cardiovascular risk is increased even further for those taking phenytoin and carbamazepine, because these medications affect the liver in a way that can cause cholesterol and triglyceride levels to increase.


2.  Nutrient deficiencies (5, 6)

Antiseizure medication can change the absorption, metabolism and/or excretion of certain nutrients, which will make it more likely for nutrient deficiencies to develop.  The nutrients at greatest risk include:

  • vitamin A
  • vitamin B1 (thiamine)
  • vitamin B2 (riboflavin)
  • vitamin B3 (niacin)
  • vitamin B6
  • vitamin B12
  • vitamin D
  • biotin
  • calcium
  • folate

While a nutritious and varied diet including vegetables, fruit, whole grains, low fat dairy products and low-fat protein foods are recommended for everyone to ensure an optimum intake of nutrients, sometimes diet is not sufficient to offset the impact of antiseizure medication and additional supplements may be required (see below).


3. Bone loss (5, 7)

Antiseizure medication can reduce bone mineral density and increase the odds of a fracture by 1.2 – 2.4 times.  This medication can negatively impact bone health in one or more of the following ways:

  • converts vitamin D to its INACTIVE form (and/or actively breaks down vitamin D).
  • causes less calcium to be absorbed from the gut (this can be due to the reduced vitamin D or other mechanisms).
  • results in higher parathyroid hormone levels (due to lower circulating calcium levels) which then results in a higher bone turnover.
  • reduces serum levels of vitamin K.
  • directly affects the function of bone cells.
  • reduces collagen synthesis.
  • alters biosynthesis, transportation and clearance of sex steroids (such as testosterone).


Top 5 recommendations for people taking antiseizure medication

1.  Monitor weight

Weight should be monitored monthly to alert clients of any medication-induced weight gain/loss which could impact their overall health and wellbeing.  Clients should be referred to a dietitian if they require additional support managing their weight.

For more information, go to our article on Medication-induced weight gain.


2. Request blood tests

  • Full blood count
  • Urea & electrolytes
  • Liver enzymes
  • Vitamin D
  • Calcium
  • Alkaline phosphatase
  • Vitamin B12/folate
  • Cholesterol
  • HbA1c

The above should be checked every 2-5 years (at a minimum) to ensure that levels stay within the optimal range and deficiencies do not develop.8   Do not skip the blood tests just because someone is taking an over-the-counter supplement — these are not always sufficient to maintain levels when someone is taking antiseizure medication.  If the blood tests come back showing levels outside of the optimum range, do make sure the GP prescribes supplements to correct the problem.

Ideally, levels of zinc, copper and selenium should also be checked periodically, as these minerals are also essential for the normal functioning of neurons.9


3. Assess fracture risk (10)

NICE guidelines for Osteoporosis – prevention of fragility fractures recommend assessing fracture risk in people taking antiseizure medication using QFracture®.  This will help health professionals decide whether a DXA scan should be considered.  Clients should be referred for a DXA scan if their 10 year fracture risk is >10%.


4.  Take calcium and vitamin D supplements (5, 10)

As outlined above, people taking antiseizure medication should also take the following supplements to reduce their fracture risk (AFTER the above blood tests have been completed):

  • 1000 – 1500mg calcium per day; AND
  • 1000 – 2000IU vitamin D per day.

5. Take folate and vitamin B12 supplements (5)

While antiseizure medication can affect several nutrients, deficiencies in vitamin D (see above), folate and vitamin B12 tend to be the most problematic.  For that reason, the following supplements are recommended (AFTER a blood test has been conducted):

  • folate – 1 mg/day (prophylactic) or 5mg/day (deficiency correction); AND
  • vitamin B12 – 15 mcg/day (prophylactic) or 900mcg/day (deficiency correction).


Dietitians can help clients arrange for blood tests, interpret the results, improve their eating habits and advise on over-the-counter supplements, all to optimise health and offset the side effects of this medication.  To refer someone with a brain injury, spinal cord injury or complex orthopaedic trauma for a comprehensive dietetic assessment, contact Specialist Nutrition Rehab at 0121 384 7087 or

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Specialist Nutrition Rehab
West Midlands
B24 0PL


07787 603 863

0121 384 7087

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