Pharmacy Diabetes


It is worth having a conversation with people who have been on metformin for long periods of time to understand if they experience intermittent diarrhoea. If people are experiencing intermittent diarrhoea, consideration should be given to metformin as the cause.  

  • If the intermittent diarrhoea is bearable and not inhibiting day to day life, then this may not require intervention.
  • If, intermittent diarrhoea is a concern for people, it is worth discussion with the prescribing doctor and/or referral to the health care team.

Metformin SR and MR are traditionally prescribed at night since the studies were conducted at this time of the day, however, the time of day is irrelevant. 

  • While not PBS listed to be taken twice a day (morning and night) this dosing is often better with respect to the gastrointestinal side effect profile.

Metformin SR or MR is designed to dissolve in the small intestine via small pellets that pass through the outer casing of the shell of the tablet/caplet. What is left to pass into the faeces is this outer shell. This often worries people since they will see the outer shell in the toilet bowl.  

  • It is often helpful to advise that the medicine itself is dissolving and working appropriately.

The effect on an individual’s blood glucose levels when beginning metformin is approximately  two weeks.  

If an individual has been asked to monitor their glucose levels at the start of metformin please let them know that metformin will take two to three weeks to impact this.

Metformin should be ceased temporarily in times of illness, when having any form of dye injected for radiological procedures, during times of dehydration or fasting and before surgery (2 days prior, during and for 2 days after). This is to protect kidney function.  

Please refer the individual to their health care team.

Metformin is known for causing malabsorption of vitamin B12. This often presents as pins and needles and numbness which can be diagnosed as peripheral neuropathy.  

  • All individuals on metformin should be supplemented with sublingual or buccal vitamin B12 (not tablets since this will not be absorbed) to prevent this.

This group of medicines are rarely used today due to the side effect profile including weight gain, peripheral oedema and increase risk of heart failure and fractures.

Thiazolidinediones should be used with caution in anyone with heart conditions.
Rosiglitazone – There is an increased risk of cardiac failure when rosiglitazone is added to treatment regimens that include insulin or sulfonylureas.

  • Annual cycle of care - Cardiac screening.
  • Diabetes MedsCheck with referral back to GP for screening.

Rosiglitazone or Pioglitazone in combination with insulin or oral hypoglycaemic agents that cause hypoglycaemia may increase the risk of low glucose levels

  • Referral for glucose monitoring
  • Referral to healthcare team for further advise on hypoglycaemia management.
  • Diabetes MedsCheck

Approximately 5% of patients using TZDs develop peripheral oedema. When used with other antidiabetic drugs, the risk of peripheral oedema increases to approximately 18%.

  • Immediate referral to health care team.
  • Diabetes MedsCheck for side effect profile.

TZD associated weight gain may result mainly from increased fat mass and fluid retention and may be in part congruent to the mechanism of action of TZD. Increases in fat mass are almost exclusively limited to subcutaneous fat.

  • Diabetes MedsCheck, with education on why weight gain is occurring.
  • Referral to healthcare team for support with healthy eating plan.

  • Cholesterol monitoring in pharmacy.
  • Diabetes MedsCheck
  • Referral to healthcare team for annual cycle of care with referral for cholesterol assessment.

TZD use leads to decreased bone mineral density (BMD) and an elevated risk of fracture.

  • Monitoring for calcium and strong bones in pharmacy.
  • Referral pathways back to GP where concerns.

There is a modest but clinically significant increase in the risk of bladder cancer with pioglitazone. This risk appears to be related to cumulative dose and duration of exposure.

  • Annual cycle of care-eye check
  • Diabetes MedsCheck referral back to GP for screening.

Increased appetite, dizziness, vertigo, flatulence, sweating, glycosuria, proteinuria and increased lactic dehydrogenase have been reported in combination with sulfonylureas.

  • Diabetes MedsCheck due to side effect profile.


Pioglitazone – There were reports of changes in liver enzymes post market.

  • It is recommended all individuals commenced on pioglitazone have liver enzymes checked before and during treatment.
  • Diabetes MedsCheck due to side effect profile.

Individuals with type 2 diabetes mellitus using TZDs have a higher incidence of diabetic macular oedema.

  • Referral to healthcare team for annual cycle of care-eye check.
  • Diabetes MedsCheck referral back to GP for screening.