Black Seed Oil Side Effects: Kidneys, Liver, Heart, Women and Medicines

Black seed oil is safe for most adults in food amounts and at the dose on the label, about 1 teaspoon a day. The most common side effects are stomach upset (nausea, bloating, heartburn, a strong aftertaste) and skin rashes when it is applied to the skin. The more serious risks are interactions: black seed oil may push blood sugar and blood pressure too low in people on medicines for them, and may increase bleeding with blood thinners. Pregnant women should avoid supplement amounts. Below are black seed oil's side effects for the kidneys, liver and heart, and for women, plus who should avoid it.

Common side effects

• Stomach upset: nausea, bloating, heartburn, burping and a peppery aftertaste. Taking it with food usually helps.
• Allergic skin reactions: black seed oil applied to the skin is a known cause of allergic contact dermatitis, an itchy, red rash. Patch test and dilute it. See black seed oil for skin.
• Throat warmth: a peppery catch in the throat is normal. Swelling, difficulty breathing or a widespread rash is not. Seek urgent care.

Black seed oil and medicines

• Diabetes medicines: black seed oil may lower blood sugar. Combined with diabetes drugs, sugar can drop too low. Watch for shakiness, sweating and confusion.
• Blood pressure medicines: it may lower blood pressure further, which can cause dizziness or fainting.
• Blood thinners and anti-platelet drugs: it may slow clotting and raise bleeding risk.
• Sedatives: it may add to drowsiness.
• Other medicines processed by the liver: interactions are possible. Ask your pharmacist.
• Before surgery: stop at least 2 weeks before planned surgery.

Black seed oil side effects on the kidneys

At normal doses, most studies haven't shown kidney harm, and some animal studies even suggest protection. But there are case reports of kidney injury in people taking black seed in supplement amounts. People searching about kidney stones should know there is no good evidence that black seed oil causes them. A small trial even studied it as a stone treatment. If you have kidney disease or a history of stones, ask your doctor before taking it daily.

Black seed oil side effects on the liver

Studies at normal doses generally haven't shown liver damage, and some animal research suggests a protective effect. Very high doses are a different matter, and supplements can be contaminated or mislabelled. If you have liver disease, or you notice yellow eyes, dark urine or pain under the right ribs, stop and see a doctor.

Black seed oil side effects on the heart

Black seed oil may modestly lower blood pressure. That is usually a hoped-for effect, but in people already on blood pressure medicine, or with low blood pressure, it can cause dizziness, light-headedness or fainting. If you have a heart condition, ask your doctor first. For other herbs Nigerians use for blood pressure, and their cautions, see herbs for high blood pressure in Nigeria.

Black seed oil side effects for women

• Pregnancy: food amounts, such as seeds in cooking, are considered fine, but supplement amounts are likely unsafe, because black seed may affect the womb's contractions. Avoid it unless your doctor approves.
• Breastfeeding: there isn't enough safety information. Ask your doctor.
• Periods and fertility: there is no good evidence that black seed oil regulates periods or boosts fertility. See a doctor about irregular periods.

How to reduce the risk of side effects

1. Stick to the label dose. The xHerbs label says 1 teaspoon daily for adults, with food or water.
2. Start with half a teaspoon for a few days.
3. Take it with food if your stomach complains.
4. Tell your doctor or pharmacist you take it, especially if you are on regular medicines.
5. Buy pure oil from a traceable seller. See how to know original black seed oil.
6. Dilute and patch test before using it on skin or hair.

Our full guide to how to use black seed oil covers honey mixes and timing.

Where to buy black seed oil, and ask questions first

• Port Harcourt: Doyen Pharmacy, beside Salvation Ministry, Okuru Link, Golf Estate Road, Golf Estate. Tel: 0815 091 0417 or 0815 091 0418. You can ask the pharmacist about your medicines.
• Lagos: Elo-Ruks Naturals, Shop E2/379, Articles Market, Abule Oshun.
• Online: xHerbs Black Seed Oil 200ml (₦15,500, October 2026).

Frequently asked questions

What are the side effects of black seed oil?

The most common are stomach upset and, on the skin, allergic rashes. It may also lower blood sugar and blood pressure and increase bleeding risk in people on related medicines.

Is black seed oil bad for the kidneys?

At normal doses, studies generally haven't shown kidney harm, but there are case reports of kidney injury with supplement use. People with kidney disease should ask a doctor first.

Can black seed oil cause kidney stones?

There is no good evidence that it does. If you have a history of stones, check with your doctor before taking it daily.

Is black seed oil safe in pregnancy?

Supplement amounts are likely unsafe in pregnancy, because black seed may affect the womb. Avoid it unless your doctor approves.

Can I take black seed oil with blood pressure or diabetes medicine?

Only with your doctor's or pharmacist's advice. It may lower blood pressure and blood sugar further.

Bottom line: Black seed oil's common side effects are stomach upset and skin rashes. The bigger risks are low blood sugar, low blood pressure and bleeding when combined with medicines, plus pregnancy. Stick to the label dose of 1 teaspoon a day with food, and ask a pharmacist first if you take regular medicine, for example at Doyen Pharmacy, Port Harcourt.