When taking weight management medication, it’s important not to overlook the impact this can have on other medications taken for other health concerns.

Here are some key points regarding other medications.

  1. Diabetes medication. Some diabetes medications can cause low blood sugar, in particular insulin, sulfonyureas, and meglitinides. As weight goes down, diabetes medication needs often decrease. Thus, low blood sugars can occur if there is a reduced need for diabetes medication, but the insulin/sulfonylurea/meglitinide is not reduced. The GLP1 based medications [Semaglutide (Wegovy/Ozempic), tirzepatide (Zepbound/Mounjaro) , and liraglutide (Saxenda)] are also diabetes medications, so even if weight is not going down, the doses of insulin/sulfonylurea/meglitinide often need to be reduced, often right from when the GLP1-based medication is started.

  2. Blood pressure medication. When people with elevated weight and hypertension (high blood pressure) lose weight, blood pressure medication needs may decrease. This is because weight loss often reduces blood pressure. Also, some of the more powerful GLP1-based medications [semaglutide (Wegovy/Ozempic), tirzepatide (Zepbound/Mounjaro)] may have some BP lowering effect independent of weight loss. So, it’s really important to monitor blood pressure when taking weight loss medication – much more on this previously blogged here. For naltrexone/bupropion (Contrave), BP tends to go up a little bit when the medication is started, but long term, the BP is usually about the same as before treatment.
  3. Thyroid hormone. Hypothyroidism (underactive thyroid) is common, and it is treated with thyroid hormone [usually levothyroxine (Synthroid/Eltroxin)]. Thyroid hormone needs usually decrease with weight loss. So, for people on thyroid hormone, thyroid blood work should be followed every couple of months while losing weight, and rechecked a month after any thyroid hormone dose change).
  4. Birth control pill [tirzepatide (Zepbound/Mounjaro only)]. The GLP1-based medications slow down the stomach, mostly during the gradual dose escalation phase of treatment. Tirzepatide slows it down enough that it substantially reduces absorption of the birth control pill. As blogged previously, the product monograph for tirzepatide recommends an alternative form of contraception, or adding a barrier method of contraception for 4 weeks after initiation and for 4 weeks after each dose escalation.
  5. Medications where levels are monitored. Levels of some medications that need to be closely regulated may change with a change in weight. This includes meds like digoxin, lithium, dilantin, valproic acid, cyclosporine, tacrolimus, carbamazepine, and others. It also includes the blood thinner warfarin, where INR (an indicator of how ‘thin’ the blood is) is monitored. Note that this is not a comprehensive list.
  6. Medication interactions. The weight management medications naltrexone/bupropion (Contrave), and phentermine/topiramate (Qsymia -not available in Canada), have a number of interactions with other meds. Orlistat (Xenical) has a few potential interactions to be aware of. The GLP1-based medications [ Semaglutide (Wegovy/Ozempic) and tirzepatide (Zepbound/Mounjaro) , and liraglutide (Saxenda)] slow the stomach, but this hasn’t typically seemed to translate to clinically relevant effects on other meds – other than tirzepatide and the birth control pill as above.
  7. Testosterone – read my full blog on this here (added august 2026).

All of the above considerations underscore why it’s so important (in my opinion) to embark on your weight loss journey with a health care professional to guide and support you. I worry about all the avenues that are popping up around the world where people can access weight management medication without health care support. Note also that the above list is not exhaustive. At a minimum, have a pharmacist go through your medications with you, and ask if there are any concerns or adjustments that need to be made, or any parameters that need to be watched.


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