SGLT2 Inhibitors and Kidneys: Questions to Ask Your Doctor
Posted 18 Sep 2026 | Source:
If you have kidney disease, or diabetes that has started to affect your kidneys, you may be on a medicine whose name ends in "-gliflozin". These are called SGLT2 inhibitors. Most people I meet have been told one thing about it: that it is a sugar tablet. That description is not wrong, but it is incomplete, and the gap causes real trouble. People stop it when they fall ill. People stop it when their sugar readings look good. Both decisions are made in good faith and both can work against you. Let me explain what I am actually prescribing it for, and what I would want you to ask me.
What it does
These medicines act in the kidney. They stop some of the glucose that has already been filtered from being reabsorbed back into your blood, so it leaves in the urine instead. That brings the blood sugar down. Separately from that sugar effect, trials have shown kidney and heart benefits in selected groups of patients.
I want you to notice that word. The benefit was shown in people who met defined entry criteria — particular ranges of kidney function, particular levels of protein in the urine, particular combinations of conditions. The patients studied in one major kidney trial were not the same as those in another.
So here is my honest summary. For some people with kidney disease, these medicines slow the decline of kidney function and reduce certain heart problems. Whether you are one of those people is a judgement I make about your situation. It is not a general rule, and I am wary of anyone who tells you it is.
Why your sugar reading is not the measure of whether it is working
Because the tablet gets introduced as a diabetes medicine, people quite reasonably conclude that once the sugar is behaving, the job is done and the tablet can go. That logic does not apply here.
When I prescribe this for kidney or heart protection, your glucose reading is not how I judge whether it is doing its work. Some of my patients who take it do not have diabetes at all.
If you are not sure which reason applies to you, that is the most useful single question you can ask me.
The creatinine rise that frightens people
When you start one of these, your blood creatinine often goes up a little and your eGFR dips over the first few weeks. I expect that. It reflects a change in the pressure inside the filtering units, and it is usually followed by a slower long-term decline than you would otherwise have had.
The problem is what happens when nobody warns you. You see the report, you conclude the medicine has damaged your kidneys, and you stop it.
So if I check your kidney function after starting, ask me what change I would consider expected and what would make me review things. Then you are not sitting at home interpreting a number on your own.
The conversation that gets missed most often
This is the one I care about most. If you become unwell — vomiting, diarrhoea, a significant fever, not eating or drinking properly — or if you are going for certain procedures or surgery, some medicines may need to be paused for a while. This one can be among them.
The advice is individual and depends on what else you take and what else you have. Get your instructions from me before you need them, and get them in writing.
Ask:
- In which situations should I stop this?
- For how long, and when do I restart?
- Whom do I contact if I am not sure?
Please do not invent your own rule. And equally, please do not push on through a severe illness simply because nobody told you otherwise.
Side effects I want you to know about
Fungal infections of the genital area and urinary tract are more common with these medicines, particularly if you have diabetes. Keeping the area clean and dry helps, and it is treatable.
Tell me about it rather than putting up with it — I have had people quietly stop an important medicine over a problem I could have sorted out in a week.
There is a rarer but more serious problem: a form of diabetic ketoacidosis that can occur even when your blood sugar is not high. What I want you to watch for is nausea and vomiting, abdominal pain, rapid breathing, and unusual drowsiness or confusion.
That combination needs urgent assessment the same day — not a wait-and-see. Ask me which symptoms should send you looking for help immediately.
When it is not the right medicine for you
Suitability depends on your kidney condition, your other health problems, what else you take, whether you are pregnant or breastfeeding, and the direction your kidney function is moving.
This is genuinely not something you can work out from an article, including this one. What I can tell you is that any article claiming everybody with kidney disease should be on one of these is going beyond what the evidence supports.
Four questions to bring me
- Why have you prescribed this for me — sugar, kidney and heart protection, or both?
- What monitoring do I need, and when is my next kidney blood test?
- What are my sick-day instructions, in writing?
- Which symptoms mean I should seek help the same day?
If you are on several medicines, bring the complete list — painkillers, ayurvedic and herbal preparations, supplements — and ask me whether anything on it interacts.
Frequently asked questions
Q: Is this only a blood sugar tablet?
A: No. Some of these medicines have kidney and heart benefits in selected people. The reason it was prescribed for you depends on your health and on which medicine you are taking.
Q: Should everyone with CKD be on one?
A: No. Suitability depends on the kidney condition, other health factors, safety considerations and your clinician's assessment.
Q: My creatinine went up after starting. Should I stop?
A: Not on your own. A small early rise is a recognised effect of starting these medicines. Contact whoever prescribed it and ask whether your change is within the expected range.
Q: Can I take it if I do not have diabetes?
A: Some people without diabetes are prescribed these for kidney or heart reasons. Whether that applies to you is a clinical decision.
Q: What should I ask before starting?
A: Why it is being prescribed, what monitoring is needed, which problems to report, and your personal instructions for when you are ill.
Call to action: Ask your prescriber for the purpose, the monitoring plan and your personalised illness instructions.
Disclaimer: General kidney education. Your tests, treatment and follow-up depend on your clinical assessment.
