15 supplement or medication combos you probably should not mix

Many of us take supplements and/or medications daily to improve our health and well-being – but taking certain pills together can create a dangerous mix.

In this post, we will show you 15 combinations of supplement/medication that shouldn’t be used together.

Let’s start.


Vitamins are a type of essential nutrients – we can’t produce them in our body and have to get from outside source.

Vitamins are generally harmless as a supplement, but if you are using some of these medications listed below, be sure to check with your doctor or pharmacist.

1. Vitamin B3 and Cholesterol lowering drugs

Vitamin B3 (Nicotinic acid or niacin) should be avoided if you are using statins, a type of cholesterol lowering medication.

Niacin is sometimes used to help lower triglycerides (a type of lipid) and raise hdl or good cholesterol. Whereas statins are normally used to lower ldl or bad cholesterol. It’s common to have high triglycerides and high bad cholesterol so this drug combination is quite common.

While this combo is effective to quickly bring down your cholesterol levels, it also increases your risk of having rhabdomyolysis – muscle breakdown. This combination is therefore not recommended.


Niacin is also known as nicotinic acid and in Malaysia, you could get them online or from GNC store.

Statins are prescription medications and can only get with doctor’s prescription. There are a few types of statins – atorvastatin (lipitor, storvas, rotaqor, caduet, ), Rosuvastatin (Crestor), Simvastatin (Zocor, Simvor, Vascor, Vytorin), Fluvastatin (Lescol), Lovastatin (Lestric), and Pravastatin (Pravachol).

2. Vitamin B3 and Red Yeast Rice

Red Yeast Rice

Red yeast rice is a common supplement here in Malaysia recommended for people with high bad cholesterol. Red yeast rice is chemically related to Lovastatin and therefore is not recommended to be used together with Niacin, unless advised by doctor.

3. Folic Acid (Vitamin B9) and Methotrexate


Methotrexate is a highly potent anti-rheumatic medication. It’s normally prescribed by specialist to treat certain types of cancer, severe psoriasis or rheumatoid arthritis.

Cancer, psoriasis and rheumatoid arthritis all have the same cause. Uncontrolled growth of cells.

Cells need folic acid to grow and form DNA. Methotrexate works by surpressing cell’s ability to absorb and use folate, and thereby controlling the rate of growth of cells. Giving folic acid to people on methotrexate will affect the effectiveness of methotrexate.


*It’s not uncommon to see people on both methotrexate and folic acid, mainly to prevent anemia or reduce the side effects of methotrexate. But that’s done under strict supervision of a specialist. Do not take folic acid supplements without consulting with your doctor first if you are using methotrexate.

4. Vitamin E and anticoagulant medications

Vitamin E may increase the effects of an anticoagulant medication called Warfarin and make you bleed more easily.

If you are using Warfarin and want to use Vitamin E, it’s best that you consult your doctor first before doing so. Dose of Warfarin might need to be adjusted if you start Vitamin E supplementation.


Orfarin or Apo-Warfarin are the two brands of Warfarin available in Malaysia

5. Vitamin K and Warfarin

Warfarin is a blood thinning medication – to make it harder for you blood to form clots. When you are on Warfarin, it’s harder for you to stop bleeding.

Vitamin K on the other hand, promotes blood clotting. Warfarin and Vitamin K therefore work against each other.

This combination should be avoided unless supervised by a specialist.


Like vitamins, minerals are also essential nutrients – we can’t produce these nutrients in our body ourselves and have to get it from outside source.

They are essential for us, but taking them as supplements have a problem. It can interfere/compete with other nutrients for absorption.*

6. Calcium and Magnesium

Calcium with Magnesium is a popular combination. There is a popular belief that calcium should be taken together with magnesium for maximum absorption.

It’s true that magnesium plays an important role in proper calcium absorption. But that doesn’t mean that you should take them both TOGETHER as in AT THE SAME TIME.

Minerals actually like calcium and magnesium actually compete with each other for absorption in our digestive system. At low doses, it should be okay to take them together but at higher doses, they should be taken at different times (at least two hours apart)

The same applies to other mineral combinations: zinc, Iron, selenium etc.

7. Calcium/Iron/Magnesium and antibiotics

Minerals such as iron and magnesium can sometimes attach to some antibiotics (i.e doxycycline, minocycline, ciprofloxacin, norfloxacin etc).

This can reduce the amount of antibiotics that eventually gets absorbed into the body and reduces its effectiveness.

As a general rule of thumb, avoid taking any medications within 2 hours of taking your mineral supplements.

8. Calcium/Iron/Magnesium and Bisphosphonates (Fosamax)

Fosamax Plus

Bisphosphonates is a class of medication normally prescribed for osteoporosis. The most common brand of bisphosphonates used here in Malaysia is Fosamax.

Due to its low bioavailability (extent of absorption by the stomach), you are normally advised to be taking bisphophonates on an empty stomach (so that nothing can compete for its absorption).

Minerals like calcium, iron and magnesium can attach to bisphosphonates and prevent it from being absorbed properly. So you should definitely avoid taking them at the same time.

Note: If you are using Fosamax or any other bisphosphonates, chances are you will be advised to take calcium too. So make sure you never take them at the same time.

Herbal supplements

9. Cranberry and medications to prevent clot

Cranberry juice is often recommended for when you have urinary tract infection. However, it’s shown to affect the effectiveness of anti-blood clot medication – Warfarin. If you are taking warfarin for thinning the blood, it’s advised that you avoid drinking cranberry juice.

10. Curcumin/Turmeric and medications that affect your brain

Turmeric is the spice that gives curry its yellow color. It has been used in India for thousands of years as a spice and medicinal herb.

Curcumin is the main active ingredient in turmeric. It has powerful anti-inflammatory effects and is a very strong antioxidant.

Turmeric/curcumin are most often used to improve general health, reduce pain and inflammation or as a general antioxidant.

Most people would benefit from curcumin supplementation, except those who are using medications to improve mood (antidepressants or antipsychotics).

If you are on antidepressant medications, check with your doctor before starting on curcumin/turmeric supplementation.

11. Black Cohosh and breast cancer medication Tamoxifen

Remifemin – Black Cohosh supplement

Tamoxifen is an anti-cancer medication used for breast cancer treatment. When you are on this medication, one of the side effects you will experience is menopausal like symptoms due to fluctuation of estrogen.

Black Cohosh is a herb best known for its use to reduce menopausal symptoms.

However, studies have found that black cohosh can actually reduce the efficacy of Tamoxifen if used together. The clinical significance of this interaction is still unknown (possibly minor), but best to check with your doctor before you start black cohosh supplementation.


The brand name of Tamoxifen in Malaysia is Nolvadex and Black cohosh is Remifemin.

12. Garlic/Ginseng/Ginkgo and blood thinning medications

I call these the three Gs – Garlic, ginseng and ginkgo. They are quite common here in Malaysia but they all have don’t go well with blood thinning medications, especially Warfarin.

Avoid this combination if you are on Warfarin, and talk to your doctor/pharmacist if you are on other blood thinning medications such as Plavix or Aspirin.

13. Ginseng and anti-diabetic medications

Some anti-diabetic medications such as diamicron or insulin can over-reduce your blood sugar and cause low blood sugar (hypoglycemia).

Symptoms of hypoglycemia are tremor or trembling, cold sweating, heart palpitations, cold hands and feet and dizziness.

Ginseng is also a herb that can lower blood sugar. So when ginseng is used together with insulin or anti-diabetic medications, the blood sugar can get so low that it becomes dangerous.

If you are on diabetic medications, and if you want to go on ginseng supplementation, make sure you know what to do if your sugar suddenly drops too low.

You should immediately consume a glucose tablet, sugary water (i.e. coca-cola), or a glass of fruit juice. These can quickly bring up your blood sugar levels. You should then follow up with eating slow-release carbohydrates such as cereals, bread or rice.

14. Echinacea and Caffeine

Echinacea is a popular supplement normally used to “boost up” our immune system. It has become very popular recently due to the CoVid-19 outbreak.

Echinacea is generally safe to use. However, studies have found that it can prolong the effect of caffeine in our body. If you use echinacea together with caffeine, you might find that the effect of the coffee is stronger or lasts longer.

Side effects of caffeine overdose include: shakiness, headache or difficulty sleeping.

15. Saw Palmetto and Finasteride, a medication for prostate

Finasteride tablets – Propecia

Finasteride is medication normally prescribed by specialist to treat enlarged prostate or a condition called (Benign Prostate Hyperplasia).

Saw palmetto is a popular supplement to help relief the symptoms of enlarged prostate.
It works in a similar manner as Finasteride and therefore the two should not be taken together.


Finasteride is available in Malaysia under the brand name of Proscar (for prostate) and Propecia (for male pattern hairloss)


Throughout my career as a pharmacist, I notice that people often treat supplements differently from medications. Compared to taking medications, they:

  1. Take supplements haphazardly – whenever they feel like it, they will take their supplements.
  2. Never research carefully before starting a supplement – people don’t spend enough time learning about their supplements before starting to take them. I think it’s also partly our (health industry’s) fault.

Here I would like to instill a mindset:

If you don’t believe that a supplement can work for you, then you shouldn’t get it in the first place. If you do feel a supplement can work for you and you are willing to give it a try, then you should treat it like a medication.

Unfortunately, unlike medications, which are more tightly regulated, there are no specialised doctors around to hand you information about supplements and teach you how to use them correctly. So you yourself will have to do the hardwork of researching.

Spend some time researching on them before you start taking them: side effects, how it works, any interactions with other medications, what is the best way to take them.

Take your supplements more seriously.