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HIGH BLOOD PRESSURE SERIES · ARTICLE 10 OF 12
High blood pressure and diabetes
The deadly duo.
High blood pressure and Type 2 diabetes are the two most common chronic conditions in South Africa. They share risk factors, they travel together through families, and they amplify each other’s damage in almost every part of the body. About two out of every three South African diabetics also have high BP. About a quarter of people diagnosed with high BP are also walking around with pre-diabetes they don’t yet know about.
If you have both, this article is for you. If you have one and someone in your family has the other, it is for you too. We are going to explain why these two conditions travel together, why they make each other worse, and the integrated plan — food, walking, medication, targets — that protects against both at the same time.
A companion to the Phila Today Diabetes Series
This article is the bridge between two of our series. We will cross-reference the Diabetes Series throughout. If you have only read the High Blood Pressure Series so far, the Diabetes Series is the natural next step.
Why these two travel together
For decades, high BP and Type 2 diabetes were treated as separate conditions that just happened to co-exist. The research of the last 30 years has shown they are deeply connected. They share a common engine called insulin resistance — the cells of the body becoming less responsive to insulin, and the body trying to compensate by producing more of it.
What insulin resistance actually does
High levels of insulin in the blood, sustained over years, do several things to BP all at once:
• They tell the kidneys to hold on to salt. More salt in the body, more water, more pressure in the arteries.
• They activate the sympathetic nervous system. This is the “fight or flight” arm of the nervous system, and it constricts blood vessels and raises heart rate.
• They cause weight gain, especially around the middle. Belly fat is itself a BP-raising organ — it produces hormones that constrict blood vessels.
• They make blood vessel walls stiffer and less responsive.
So before either diabetes or high BP is diagnosable on a test, the engine driving both is already running. This is why so many people develop both within a few years of each other — and why making a change for one almost always helps the other.
The shared risk factors
Both conditions have an almost identical list of “people who tend to get this”:
• Age over 40
• Family history
• Black South African ancestry — both conditions are more common and develop earlier
• Carrying extra weight, especially around the middle
• A diet high in salt, sugar and refined carbohydrates
• Sedentary lifestyle
• Long-term stress
• Poor sleep, especially sleep apnoea
If you have any three of these, the chances that you have both conditions, or will develop both, are high.
How they amplify each other’s damage
This is the part that matters most. High BP on its own damages organs. Diabetes on its own damages organs. The two together damage organs faster, more severely, and in more places than either alone. The combined risk is not 1 + 1 = 2; it is closer to 1 + 1 = 4.
The kidneys
Diabetes is the single biggest cause of chronic kidney disease in South Africa. High BP is the second biggest. People with both develop kidney disease at much higher rates — and progress to dialysis years earlier — than people with either condition alone.
The good news: Two specific drug groups (ACE inhibitors and ARBs — article 9) are particularly good at protecting the kidneys in people with both conditions. This is why almost every diabetic with high BP in South Africa is on one of them.
The eyes
Both conditions damage the small blood vessels at the back of the eye. Diabetic retinopathy is the most common cause of new blindness in working-age South Africans. Hypertensive retinopathy compounds it. Annual eye exams matter doubly when you have both.
The good news: If both BP and blood sugar are well controlled, the rate of retinopathy progression slows dramatically. Many South Africans with both conditions never lose meaningful vision.
The heart
People with both diabetes and high BP have 2 to 4 times the risk of heart attack compared with the general population. Heart failure is also more common, and develops earlier. Coronary artery disease tends to be more diffuse — affecting more of the heart’s blood vessels at the same time — which makes it harder to treat with surgery or stents alone.
The good news: Aggressive treatment of both — BP below 130 / 80, HbA1c below 7%, and statin therapy in most cases — cuts that doubled risk back almost to normal over 10 years.
The brain
Diabetes triples stroke risk on its own. Adding high BP roughly doubles it again. Vascular dementia is also more common, more severe, and tends to start earlier in people with both conditions than in those with either alone.
The good news: Stroke risk responds dramatically to BP control. Bringing systolic BP down by 10 mmHg cuts stroke risk by 30%, and the effect is biggest in people who started with both conditions.
The feet
Diabetic neuropathy (nerve damage) plus high-BP-driven artery damage is the combination that leads to most diabetic foot amputations in South Africa. The nerve damage means you can’t feel an injury; the artery damage means the injury can’t heal. Together they are a slow disaster.
The good news: Daily foot checks (Diabetes Series article 9), well-controlled BP, well-controlled blood sugar, and annual clinic foot exams together prevent most foot complications.
The integrated targets
When you have both conditions, your clinic will push for tighter numbers than for either alone. The reasoning is that the combined damage is bigger, so the protection from tight control is bigger too.
Number Target for both conditions Blood pressure Below 130 / 80 mmHg HbA1c (3-month blood sugar average) Below 7% for most adults, below 6.5% if achievable without hypos Fasting blood sugar 4 – 7 mmol/L LDL cholesterol Below 1.8 mmol/L (most patients will be on a statin) Waist circumference Below 94 cm for men, below 80 cm for women Annual urine protein Negative (any protein needs investigation)
These targets are not arbitrary. Each one is the level at which large clinical trials have shown the biggest reduction in stroke, heart attack, kidney failure and amputation risk in people with both conditions.
The one habit set that helps both
The remarkable thing about having both conditions is that almost everything that lowers BP also lowers blood sugar. The food list from article 5 of this series and Diabetes Series article 3 overlap almost entirely. The walking plan in article 7 is the same plan as in Diabetes Series article 5. The salt advice in article 6 is also good diabetes advice. The sleep, stress and alcohol guidance in article 8 applies word-for-word.
If you have both, you don’t have to follow two diets, two exercise plans, two lifestyles. You follow one:
• Eat from the BP food list (article 5): beans, beetroot, bananas, oats, sweet potato, morogo, garlic, amasi, pilchards, unsalted nuts.
• Cut salt (article 6) and sugar in equal measure. Bread, processed meats, stock cubes, sugary drinks, sweets — these damage both conditions.
• Walk 30 minutes briskly, 5 days a week (article 7). This lowers BP by 5 – 8 mmHg and HbA1c by 0.5 – 1%. Almost no other single intervention does both at once.
• Sleep at least 7 hours, treat sleep apnoea if present (article 8). Both conditions respond.
• Limit alcohol; quit smoking; manage stress.
• Take both sets of medication every day, for life.
Medication when you have both
The five BP drug groups from article 9 all work in diabetics. Some are better suited than others.
First choice in most diabetics: ACE inhibitor or ARB
These are recommended for almost every diabetic with high BP. The reason is the kidney protection — they slow the progression of diabetic kidney disease beyond what the BP reduction alone would predict. Even diabetics without overt kidney problems benefit. This is one of the clearest “right drug for the right patient” stories in medicine.
Second drug, usually: calcium channel blocker (amlodipine)
Calcium channel blockers don’t affect blood sugar at all and combine well with ACE inhibitors or ARBs. This is the standard two-drug combination for diabetics with high BP in South Africa.
Diuretics — useful but with awareness
Thiazide diuretics like HCTZ can slightly raise blood sugar levels, particularly at high doses. At the lower doses now used in routine BP treatment, this effect is usually small and clinically unimportant. Many South African diabetics are on a diuretic without any sugar control problem.
Beta-blockers — use with care
Beta-blockers can mask the warning signs of a hypoglycaemic episode (a “hypo”) — the racing heart, the trembling, the anxiety — because they block exactly those responses. People with diabetes on insulin or sulphonylurea tablets, who are prone to hypos, need to know this. Sweating, hunger and confusion are still present as hypo warning signs, but the heart-pounding alarm is muted.
Newer drugs — SGLT2 inhibitors
A relatively newer group of diabetes drugs, called SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin), brings down blood sugar by making the kidneys excrete extra glucose in the urine. They also bring BP down by about 4 – 5 mmHg, reduce the progression of kidney disease, and reduce heart failure admissions. They are an excellent choice for many diabetics with high BP — but they are not yet on the South African public-sector essential medicines list for general use. Discuss them with your private doctor or specialist clinic.
The “one tablet, two conditions” strategy
Many South African diabetics with high BP end up on a regimen something like: one ACE inhibitor or ARB (BP + kidney protection), one calcium channel blocker (BP), one statin (cholesterol + arteries), metformin (blood sugar), and possibly aspirin (clot prevention). It looks like a lot. But each tablet is doing a specific protective job, and combined-dose pills can cut the count down. Ask your clinic about combination tablets if your handful is getting unwieldy.
What the integrated clinic visit looks like
In a well-run public clinic, a diabetic with high BP is in a “chronic care” track that bundles everything into one visit, usually every 1 – 3 months. A typical visit includes:
• Blood pressure, weight, sometimes waist measurement
• A finger-prick blood sugar check, plus an HbA1c every 3 – 6 months
• A urine dipstick check for protein
• A foot exam (sometimes annual, sometimes every visit, depending on risk)
• A review of medication adherence and side effects
• A monthly prescription refill from the clinic pharmacy
Once a year, you should also have your kidney function tested with a blood draw (creatinine and eGFR), your cholesterol tested, and an eye exam from an optometrist or ophthalmologist. Both conditions deserve annual blood work and an annual eye check, ideally during the same visit.
What to ask at your next visit
If you have both conditions, the following questions are reasonable to bring to a clinic visit:
• “What was my last BP reading and is it on target (under 130 / 80)?”
• “What was my last HbA1c and is it on target (under 7%)?”
• “When was my last kidney function blood test?”
• “When was my last urine dipstick check?”
• “When was my last eye check?”
• “Am I on an ACE inhibitor or ARB? If not, why not?”
• “Can any of my tablets be combined into a single pill?”
• “What’s my next target? When should I come back?”
None of these are demanding questions. They are the questions you would ask if you were a junior doctor reviewing the case. Your clinic will appreciate that you know what you are asking about — it makes their job easier and your care better.
The bigger picture
Having both high blood pressure and diabetes is not the bad luck it can feel like. The two travel together because they share a cause; they damage organs in the same places because they target the same kinds of blood vessels; and — most importantly — they respond to the same kinds of treatment. Almost every single thing you do to manage one will help the other.
Patients who treat both conditions well in their forties and fifties end up, on average, with as much healthy time ahead of them as people who never had either. The two conditions together do not have to be a slow road to amputation, dialysis, blindness and stroke. With careful, consistent, ordinary care — and the support of an SA public clinic that is well used to managing both — they can be a manageable, long-lived background condition.
The next article in the series moves to a specific population: pregnant women. High BP in pregnancy is its own urgent topic, with its own warning signs, its own treatment considerations, and its own checklist.
Where to get more help
Diabetes South Africa — diabetessa.org.za · 011 792 9888 — patient information, support groups, dietitian referrals.
Heart and Stroke Foundation South Africa — heartfoundation.co.za · 021 422 1586.
Your nearest public clinic chronic-care team — designed exactly for people with both conditions. Ask to be registered if you aren't already.
Phila Today Diabetes Series — companion reading. All 17 articles are now available in the Phila Today archive.
Phila Today High Blood Pressure Series — next: high blood pressure in pregnancy — pre-eclampsia and what to watch for.
Phila Today · Article 10 of 12 in the High Blood Pressure Series