Supplements and medication interactions after 50: what to avoid, what to space out and how to get a medicines review

Why supplement and medicine interactions matter more after 50

Picture a kitchen drawer in Leeds: blood pressure tablets, a statin, omeprazole for heartburn, and a tub of “joint support” a neighbour recommended. Each made sense when it arrived. Nobody has looked at them together.

That’s polypharmacy (taking several medicines at once), and it’s the norm later in life. According to the MSD Manual, about 90% of older adults take at least one prescription medicine regularly, and 43% take five or more. Add vitamins and herbal products and the numbers climb higher.

Age also changes how the body handles medicines:

• there’s less water and muscle in the body and more fat, so some medicines reach higher levels;
• the kidneys clear medicines into urine less well;
• the liver breaks many medicines down more slowly.

So medicines stay in the body longer, and side effects become more likely. A supplement that was harmless at 40 can tip the balance at 75.

Supplements get in the way of medicines in four main ways:

1. They block absorption. Calcium, iron, magnesium and zinc bind some medicines in the gut: levothyroxine, certain antibiotics and bisphosphonates.
2. They add to the effect. Ginkgo with blood thinners raises bleeding risk. Berberine with diabetes medicines can push blood sugar too low.
3. They weaken the medicine. St John’s wort lowers the effect of warfarin and many other medicines. Vitamin K works against warfarin.
4. The medicine drains a nutrient. Metformin and long-term proton pump inhibitors (PPIs, such as omeprazole) lower B12. PPIs taken for more than a year can lower magnesium.

Supplements and medicines: a table by medicine group

The table covers the medicines most often prescribed after 50. “Avoid” means don’t combine unless your doctor says so. “Space out” means take them at different times. “Ask” means the pair can work, but your GP or pharmacist should know about it.

If you’d rather look up one group at a time, pick it here:

For the timing of minerals, our vitamin compatibility chart gives the gaps pair by pair.

Supplements and statins

Statins are among the most common medicines after 50, and most everyday vitamins sit alongside them without trouble. Two products need care. Red yeast rice contains a substance that works like a statin, so taking both doubles up. St John’s wort, like grapefruit juice, can stop a statin working properly or make side effects more likely, says the NHS.

CoQ10 is sold for aching muscles on statins. The trials disagree, so see our CoQ10 and statins guide before you spend money on it.

Blood thinners: the combinations to take most seriously

Warfarin and the newer anticoagulants (apixaban, rivaroxaban, dabigatran) are where a supplement can do real harm. The NHS says not to take St John’s wort or vitamin K supplements with warfarin. Ginkgo raises bleeding risk with anticoagulants; our ginkgo side effects guide has the details.

Know the warning signs of bleeding listed by the NHS:

• blood in your pee or poo;
• unexplained bruising or nosebleeds;
• coughing up or vomiting blood;
• a sudden bad headache with confusion, slurred speech or weakness in an arm or leg – call 999.

For the other signs, the NHS advises calling 111 straight away.

Food matters too. Leafy greens are rich in vitamin K. You can still eat them on warfarin, but keep the amount fairly steady and ask your anticoagulation clinic.

Before you add a supplement

These steps take ten minutes and save most of the trouble:

Two common slips are easy to miss. A multivitamin often already holds calcium, iron, zinc and vitamin D, so a separate tub doubles the dose. And “natural” doesn’t mean it can’t interact. The NIA warns that combining some prescription medicines with supplements can be dangerous.

Metformin users and people on long-term acid reducers should read our vitamin B12 guide before buying. Berberine and chromium are covered in berberine side effects and chromium picolinate.

How to get a medicines review (NHS structured medication review)

NICE describes a structured medication review as a careful look at everything you take, aimed at agreeing what’s worth continuing. It covers prescribed medicines, things bought over the counter and complementary products. NICE suggests reviews for people taking several medicines, people with long-term conditions and older people. The review may be led by a pharmacist.

How to get one:

1. Ask your GP surgery for a structured medication review. Many practices have a pharmacist who runs them.
2. Bring every box and bottle, or a full list with doses, times and who prescribed each one. Our printable medicines list for your GP does this and flags pairs worth asking about.
3. Say what bothers you: side effects, too many tablets, trouble swallowing, cost.
4. Ask the key question: “Do I still need all of these?”
5. After the review, update your list and your weekly pill chart.

Between reviews, use one pharmacy if you can, so the pharmacist sees your whole record. If you use several, show your list at each one, as the NIA advises.

When to speak to a doctor straight away

• Signs of bleeding on a blood thinner (see above).
• Muscle weakness, tiredness, numbness or an irregular heartbeat on spironolactone or an ACE inhibitor: these can be signs of high potassium.
• Signs of low blood sugar on diabetes medicines after starting berberine or chromium.
• Any new problem with your medicines after starting a supplement. The NIA advises calling your doctor right away rather than waiting.

If you have kidney disease, minerals such as magnesium and potassium can build up. See supplements and kidney disease before taking any.

How to choose supplements on iHerb if you take medicines

1. Choose single-ingredient products. They’re easier to time and easier to stop if something goes wrong.
2. Skip “complexes” that hide ginkgo, St John’s wort or turmeric among vitamins.
3. Add up calcium, iron, zinc and vitamin D from every bottle, including your multivitamin.
4. Look for an independent quality mark such as USP Verified.
5. Show the label to your pharmacist before the first dose.

For what’s generally worth taking after 50, see vitamins for over 50s, or take our vitamin check.